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Configuring IS-IS Protocol

Sample Chapter is provided courtesy of Cisco Press.
Date: Mar 21, 2003.

Chapter Information

Overview of OSI Protocols and IS-IS Routing
Operation of IS-IS for CLNS/CLNP
IP and OSI Routing with Integrated IS-IS
Basic Integrated IS-IS Router Configuration
Modeling WAN Networks in Integrated IS-IS
Summary
Configuration Exercise: Configuring a Multiarea IS-IS Network
Answers to Configuration Exercise: Configuring a Multiarea IS-IS Network

Chapter Description

This supplemental material provides an overview of Intermediate System-to-Intermediate System (IS-IS) technology and its structures and protocols, along with basic configuration examples.

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Answers to Configuration Exercise: Configuring a Multiarea IS-IS Network

This section provides the answers to the questions in the configuration exercise. The answers are in bold.

Answers to Setup

To set up, do the following:

Step 1 Disable OSPF on all the routers within your pod.

The following example shows how to perform the required setup on the pod 1 routers.

p1r1(config)#no router ospf 200

p1r2(config)#no router ospf 200

p1r3(config)#no router ospf 200

Step 2 Shut the pxr1 S3 interface.

The following example shows how to perform the required setup on the p1r1 router.

p1r1(config)#int s3
p1r1(config-if)#shutdown

Answers to Task 1: Enabling IS-IS Within Your Pod

Complete the following steps:

Step 1 Enable IS-IS on the pxr1, pxr2, and pxr3 routers within your pod.

Step 2 Configure the pxr1, pxr2, and pxr3 routers within your pod with the IS-IS NETs shown in the following table.

Pod	pxr1 NET	pxr2 NET	pxr3 NET
1	00.0001.1111.1111.1111.00	00.0001.1212.1212.1212.00	00.0001.1313.1313.1313.00
2	00.0002.2121.2121.2121.00	00.0002.2222.2222.2222.00	00.0002.2323.2323.2323.00
3	00.0003.3131.3131.3131.00	00.0003.3232.3232.3232.00	00.0003.3333.3333.3333.00
4	00.0004.4141.4141.4141.00	00.0004.4242.4242.4242.00	00.0004.4343.4343.4343.00
5	00.0005.5151.5151.5151.00	00.0005.5252.5252.5252.00	00.0005.5353.5353.5353.00
6	00.0006.6161.6161.6161.00	00.0006.6262.6262.6262.00	00.0006.6363.6363.6363.00
7	00.0007.7171.7171.7171.00	00.0007.7272.7272.7272.00	00.0007.7373.7373.7373.00
8	00.0008.8181.8181.8181.00	00.0008.8282.8282.8282.00	00.0008.8383.8383.8383.00
9	00.0009.9191.9191.9191.00	00.0009.9292.9292.9292.00	00.0009.9393.9393.9393.00
10	00.0010.A1A1.A1A1.A1A1.00	00.0010.A2A2.A2A2.A2A2.00	00.0010.A3A3.A3A3.A3A3.00
11	00.0011.B1B1.B1B1.B1B1.00	00.0011.B2B2.B2B2.B2B2.00	00.0011.B3B3.B3B3.B3B3.00
12	00.0012.C1C1.C1C1.C1C1.00	00.0012.C2C2.C2C2.C2C2.00	00.0012.C3C3.C3C3.C3C3.00

The following example shows how to enable IS-IS and configure the NETs on the pod 1 routers.

p1r1(config)#router isis
p1r1(config-router)#net 00.0001.1111.1111.1111.00

p1r2(config)#router isis
p1r2(config-router)#net 00.0001.1212.1212.1212.00

p1r3(config)#router isis
p1r3(config-router)#net 00.0001.1313.1313.1313.00

NOTE

The backbone_r1 router is configured with a NET of 00.0013.1111.2222.3333.00.

Step 3 Enable IS-IS on the interfaces specified in the following table on the pxr1, pxr2, and pxr3 routers within your pod.

Router	Interfaces on Which to Enable IS-IS
pxr1	S0	S1	S2
pxr2	S0	S1	E0	Loopback10
pxr3	S0	E0	Loopback11	Loopback12	Loopback13

NOTE

For this task, the pxr1 S3 interface is shut down.

The following example shows how to enable IS-IS on the appropriate interfaces of the pod 1 routers.

p1r1(config)#int s0
p1r1(config-if)#ip router isis
p1r1(config-if)#exit
p1r1(config)#int s1
p1r1(config-if)#ip router isis
p1r1(config-if)#exit
p1r1(config)#int s2
p1r1(config-if)#ip router isis
p1r1(config-if)#exit
p1r1(config)#

p1r2(config)#int s0
p1r2(config-if)#ip router isis
p1r2(config-if)#exit
p1r2(config)#int s1
p1r2(config-if)#ip router isis
p1r2(config-if)#exit
p1r2(config)#int e0
p1r2(config-if)#ip router isis
p1r2(config-if)#exit
p1r2(config)#int loopback 10
p1r2(config-if)#ip router isis
p1r2(config-if)#exit
p1r2(config)#

p1r3(config)#int s0
p1r3(config-if)#ip router isis
p1r3(config-if)#exit
p1r3(config)#int e0
p1r3(config-if)#ip router isis
p1r3(config-if)#exit
p1r3(config)#int loopback 11
p1r3(config-if)#ip router isis
p1r3(config-if)#exit
p1r3(config)#int loopback 12
p1r3(config-if)#ip router isis
p1r3(config-if)#exit
p1r3(config)#int loopback 13
p1r3(config-if)#ip router isis
p1r3(config-if)#exit
p1r3(config)#

Step 4 Display the routing table of the pxr1, pxr2, and pxr3 routers within your pod, and verify that you have full connectivity within your pod.

The following example output is from the p1r1 router:

p1r1#show ip route
<output omitted>
Gateway of last resort is not set

   172.26.0.0/28 is subnetted, 3 subnets
i L1  172.26.1.48 [115/20] via 192.168.1.50, Serial2
i L1  172.26.1.32 [115/20] via 192.168.1.50, Serial2
i L1  172.26.1.16 [115/20] via 192.168.1.50, Serial2
   192.168.1.0/28 is subnetted, 4 subnets
i L1  192.168.1.64 [115/20] via 192.168.1.34, Serial1
           [115/20] via 192.168.1.18, Serial0
           [115/20] via 192.168.1.50, Serial2
C    192.168.1.32 is directly connected, Serial1
C    192.168.1.48 is directly connected, Serial2
C    192.168.1.16 is directly connected, Serial0
i L1 192.168.101.0/24 [115/20] via 192.168.1.34, Serial1
           [115/20] via 192.168.1.18, Serial0
p1r1#

The following example output is from the p1r2 router:

p1r2#show ip route
<output omitted>
Gateway of last resort is not set

   172.26.0.0/28 is subnetted, 3 subnets
i L1  172.26.1.48 [115/20] via 192.168.1.66, Ethernet0
i L1  172.26.1.32 [115/20] via 192.168.1.66, Ethernet0
i L1  172.26.1.16 [115/20] via 192.168.1.66, Ethernet0
   192.168.1.0/28 is subnetted, 4 subnets
C    192.168.1.64 is directly connected, Ethernet0
C    192.168.1.32 is directly connected, Serial1
i L1  192.168.1.48 [115/20] via 192.168.1.33, Serial1
           [115/20] via 192.168.1.17, Serial0
           [115/20] via 192.168.1.66, Ethernet0
C    192.168.1.16 is directly connected, Serial0
C  192.168.101.0/24 is directly connected, Loopback10
p1r2#

The following example output is from the p1r3 router:

p1r3#show ip route
<output omitted>
Gateway of last resort is not set

   172.26.0.0/28 is subnetted, 3 subnets
C    172.26.1.48 is directly connected, Loopback13
C    172.26.1.32 is directly connected, Loopback12
C    172.26.1.16 is directly connected, Loopback11
   192.168.1.0/28 is subnetted, 4 subnets
C    192.168.1.64 is directly connected, Ethernet0
i L1  192.168.1.32 [115/20] via 192.168.1.65, Ethernet0
           [115/20] via 192.168.1.49, Serial0
C    192.168.1.48 is directly connected, Serial0
i L1  192.168.1.16 [115/20] via 192.168.1.65, Ethernet0
           [115/20] via 192.168.1.49, Serial0
i L1 192.168.101.0/24 [115/20] via 192.168.1.65, Ethernet0
p1r3#

These examples show that there is full connectivity within pod 1.

Step 5 Examine the pxr1 routing table and answer the following questions:

The following example output is from the p1r1 router:

p1r1#show ip route
<output omitted>
Gateway of last resort is not set

   172.26.0.0/28 is subnetted, 3 subnets
i L1  172.26.1.48 [115/20] via 192.168.1.50, Serial2
i L1  172.26.1.32 [115/20] via 192.168.1.50, Serial2
i L1  172.26.1.16 [115/20] via 192.168.1.50, Serial2
   192.168.1.0/28 is subnetted, 4 subnets
i L1  192.168.1.64 [115/20] via 192.168.1.34, Serial1
           [115/20] via 192.168.1.18, Serial0
           [115/20] via 192.168.1.50, Serial2
C    192.168.1.32 is directly connected, Serial1
C    192.168.1.48 is directly connected, Serial2
C    192.168.1.16 is directly connected, Serial0
i L1 192.168.101.0/24 [115/20] via 192.168.1.34, Serial1
           [115/20] via 192.168.1.18, Serial0
p1r1#

Does IS-IS load-balance by default?

Yes, it does load-balance by default. In the previous example routing table, there are three equal-cost routes to 192.168.1.64 and two equal-cost routes to 192.168.101.0.

What is the IS-IS routing metric based on by default?

The default metric is a scalar cost where 1 hop = 10. Note that you count one hop for yourself or for the link (that is, the metric is always at least 20 for nonconnected networks).

Use the show clns int s0 command to determine the Level 1 and Level 2 default metric.

The following example output is from the p1r1 router:

p1r1#show clns int s0
Serial0 is up, line protocol is up
 Checksums enabled, MTU 1500, Encapsulation HDLC
 ERPDUs enabled, min. interval 10 msec.
 RDPDUs enabled, min. interval 100 msec., Addr Mask enabled
 Congestion Experienced bit set at 4 packets
 CLNS fast switching enabled
 CLNS SSE switching disabled
 DEC compatibility mode OFF for this interface
 Next ESH/ISH in 18 seconds
 Routing Protocol: IS-IS
  Circuit Type: level-1-2
  Interface number 0x0, local circuit ID 0x100
  Level-1 Metric: 10, Priority: 64, Circuit ID: 1212.1212.1212.00
  Number of active level-1 adjacencies: 1
  Level-2 Metric: 10, Priority: 64, Circuit ID: 1111.1111.1111.00
  Number of active level-2 adjacencies: 1
  Next IS-IS Hello in 5 seconds
p1r1#

The Level 1 and Level 2 default metric is 10.

What is the default administrative distance of IS-IS routes?

The following example output is from the p1r1 router:

p1r1#show ip protocols
Routing Protocol is "isis"
 Sending updates every 0 seconds
 Invalid after 0 seconds, hold down 0, flushed after 0
 Outgoing update filter list for all interfaces is
 Incoming update filter list for all interfaces is
 Redistributing: isis
 Address Summarization:
  None
 Routing for Networks:
  Serial0
  Serial1
  Serial2
 Routing Information Sources:
  Gateway     Distance   Last Update
  192.168.1.34     115   00:04:09
  192.168.1.50     115   00:03:21
  192.168.101.101   115   00:03:06
  172.26.1.17     115   00:03:11
 Distance: (default is 115)

This output shows that the default IP administrative distance is 115.

Step 6 Save the current configurations of all the routers within your pod to NVRAM.

The following example shows how to save the configuration of the p1r1 router using the copy run start command (this is an abbreviated form of the copy running-config startup-config command):

p1r1#copy run start
Destination filename [startup-config]?
Building configuration...
p1r1#

Answers to Task 2: Enabling Connectivity to the backbone_r1 Router

Complete the following steps:

Step 1 No shut the S3 interface on the pxr1 router.

Step 2 Enable IS-IS on the S3 interface on the pxr1.

The following example shows the configuration of the p1r1 router. The output from the router is also displayed:

p1r1(config)#int s3
p1r1(config-if)#no shutdown
p1r1(config-if)#
08:36:18: %LINK-3-UPDOWN: Interface Serial3, changed state to up
p1r1(config-if)#
08:36:19: %LINEPROTO-5-UPDOWN: Line protocol on Interface Serial3, changed state to up
p1r1(config-if)#ip router isis
p1r1(config-if)#^Z
p1r1#

Step 3 Display the routing table of the pxr1, pxr2, and pxr3 routers within your pod, and verify that you have full connectivity to the backbone_r1 router.

The following example output is from the p1r1 router:

p1r1#show ip route
<output omitted>
Gateway of last resort is not set

   172.16.0.0/24 is subnetted, 2 subnets
i L2  172.16.10.0 [115/20] via 10.1.1.100, Serial3
i L2  172.16.11.0 [115/20] via 10.1.1.100, Serial3
   172.26.0.0/28 is subnetted, 3 subnets
i L1  172.26.1.48 [115/20] via 192.168.1.50, Serial2
i L1  172.26.1.32 [115/20] via 192.168.1.50, Serial2
i L1  172.26.1.16 [115/20] via 192.168.1.50, Serial2
   10.0.0.0/24 is subnetted, 1 subnets
C    10.1.1.0 is directly connected, Serial3
   192.168.1.0/28 is subnetted, 4 subnets
i L1  192.168.1.64 [115/20] via 192.168.1.34, Serial1
           [115/20] via 192.168.1.18, Serial0
           [115/20] via 192.168.1.50, Serial2
C    192.168.1.32 is directly connected, Serial1
C    192.168.1.48 is directly connected, Serial2
C    192.168.1.16 is directly connected, Serial0
i L1 192.168.101.0/24 [115/20] via 192.168.1.34, Serial1
           [115/20] via 192.168.1.18, Serial0
p1r1#

The following example output is from the p1r2 router:

p1r2#show ip route
<output omitted>
Gateway of last resort is not set

   172.16.0.0/24 is subnetted, 2 subnets
i L2  172.16.10.0 [115/30] via 192.168.1.33, Serial1
          [115/30] via 192.168.1.17, Serial0
i L2  172.16.11.0 [115/30] via 192.168.1.33, Serial1
          [115/30] via 192.168.1.17, Serial0
   172.26.0.0/28 is subnetted, 3 subnets
i L1  172.26.1.48 [115/20] via 192.168.1.66, Ethernet0
i L1  172.26.1.32 [115/20] via 192.168.1.66, Ethernet0
i L1  172.26.1.16 [115/20] via 192.168.1.66, Ethernet0
   10.0.0.0/24 is subnetted, 1 subnets
i L1  10.1.1.0 [115/20] via 192.168.1.33, Serial1
         [115/20] via 192.168.1.17, Serial0
   192.168.1.0/28 is subnetted, 4 subnets
C    192.168.1.64 is directly connected, Ethernet0
C    192.168.1.32 is directly connected, Serial1
i L1  192.168.1.48 [115/20] via 192.168.1.33, Serial1
           [115/20] via 192.168.1.17, Serial0
           [115/20] via 192.168.1.66, Ethernet0
C    192.168.1.16 is directly connected, Serial0
C  192.168.101.0/24 is directly connected, Loopback10
p1r2#

The following example output is from the p1r3 router:

p1r3#show ip route
<output omitted>
Gateway of last resort is not set

   172.16.0.0/24 is subnetted, 2 subnets
i L2  172.16.10.0 [115/30] via 192.168.1.49, Serial0
i L2  172.16.11.0 [115/30] via 192.168.1.49, Serial0
   172.26.0.0/28 is subnetted, 3 subnets
C    172.26.1.48 is directly connected, Loopback13
C    172.26.1.32 is directly connected, Loopback12
C    172.26.1.16 is directly connected, Loopback11
   10.0.0.0/24 is subnetted, 1 subnets
i L1  10.1.1.0 [115/20] via 192.168.1.49, Serial0
   192.168.1.0/28 is subnetted, 4 subnets
C    192.168.1.64 is directly connected, Ethernet0
i L1  192.168.1.32 [115/20] via 192.168.1.65, Ethernet0
           [115/20] via 192.168.1.49, Serial0
C    192.168.1.48 is directly connected, Serial0
i L1  192.168.1.16 [115/20] via 192.168.1.65, Ethernet0
           [115/20] via 192.168.1.49, Serial0
i L1 192.168.101.0/24 [115/20] via 192.168.1.65, Ethernet0
p1r3#

Do you see the backbone_r1 router's loopback interfaces in your routing table? (Note that you also might see routes to the other pods.)

Yes, the backbone_r1 loopback interfaces on networks 172.16.10.0 and 172.16.11.0 are visible in all the routing tables.

Does IS-IS perform autosummarization across the network boundary by default?

No, IS-IS does not perform autosummarization across the network boundary by default. The routing tables show all configured subnets of all networks.

Does IS-IS use the same default administrative distance for Level 1 and Level 2 routes?

Yes, IS-IS uses the same default admin distance for Level 1 and Level 2: 115.

Make sure you can ping the loopback interfaces on the backbone_r1 router from the pxr1, pxr2, and pxr3 routers within your pod.

The following examples are the results of the ping commands on the pod 1 routers to the backbone_r1 router's loopback interfaces. All pings are successful:

p1r1#ping 172.16.10.100

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 172.16.10.100, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 32/32/32 ms
p1r1#ping 172.16.11.100

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 172.16.11.100, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 32/32/32 ms
p1r1#

p1r2#ping 172.16.10.100

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 172.16.10.100, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 60/60/64 ms
p1r2#ping 172.16.11.100

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 172.16.11.100, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 60/60/64 ms
p1r2#

p1r3#ping 172.16.10.100

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 172.16.10.100, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 56/59/60 ms
p1r3#ping 172.16.11.100

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 172.16.11.100, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 60/62/72 ms
p1r3#

Step 4 Save the current configurations of all the routers within your pod to NVRAM.

The following example shows how to save the configuration of the p1r1 router using the copy run start command (this is an abbreviated form of the copy running-config startup-config command):

p1r1#copy run start
Destination filename [startup-config]?
Building configuration...
p1r1#

Answers to Task 3: Changing the IS-IS Router Type

Complete the following steps:

Step 1 By default, the pxr1, pxr2, and pxr3 routers within your pod are what type of IS-IS router (Level 1, Level 2, or Level 1–2)?

What command can be used to determine the IS-IS router type?

The show clns is-neighbors command can be used to determine the IS-IS router type. The output from this command on the p1r1 router is shown here:

p1r1#show clns is-neighbors

System Id   Interface  State Type Priority Circuit Id     Format
1212.1212.1212 Se1     Up   L1L2 0 /0   01       Phase V
1212.1212.1212 Se0     Up   L1L2 0 /0   00       Phase V
1313.1313.1313 Se2     Up   L1L2 0 /0   00       Phase V
1111.2222.3333 Se3     Up   L2  0     00       Phase V
p1r1#

By default, the routers are Level 1–2 (L1L2) routers. Note that the backbone_r1 router has a command to make it a Level 2–only router.

Step 2 Examine the IS-IS link state database of the pxr1, pxr2, and pxr3 routers within your pod. Do you see both the Level 1 and Level 2 link-state database on all the routers?

The following example output is from the p1r1 router:

p1r1#show isis database
IS-IS Level-1 Link State Database
LSPID         LSP Seq Num LSP Checksum LSP Holdtime   ATT/P/OL
1111.1111.1111.00-00* 0x00000008  0x0B2C    838        1/0/0
1212.1212.1212.00-00 0x00000007  0x1C1C    839        1/0/0
1212.1212.1212.01-00 0x00000002  0xD237    434        0/0/0
1212.1212.1212.02-00 0x00000002  0xA265    1125       0/0/0
1313.1313.1313.00-00 0x00000009  0xBCB1    839        1/0/0
1313.1313.1313.01-00 0x00000001  0x4840    0 (441)      0/0/0
1313.1313.1313.02-00 0x00000002  0xA853    1117       0/0/0
1313.1313.1313.03-00 0x00000002  0xA159    1140       0/0/0
1313.1313.1313.04-00 0x00000001  0x9C5E    449        0/0/0

IS-IS Level-2 Link State Database
LSPID         LSP Seq Num LSP Checksum LSP Holdtime   ATT/P/OL
1111.1111.1111.00-00* 0x0000000C  0xDAD4    827        0/0/0
1111.2222.3333.00-00 0x00000006  0x352F    826        0/0/0
1212.1212.1212.00-00 0x0000000A  0x6588    828        0/0/0
1212.1212.1212.01-00 0x00000003  0x6031    1115       0/0/0
1313.1313.1313.00-00 0x0000000A  0xEA43    828        0/0/0
1313.1313.1313.01-00 0x00000002  0x4641    0 (441)      0/0/0
p1r1#

The following example output is from the p1r2 router:

p1r2#show isis database
IS-IS Level-1 Link State Database
LSPID         LSP Seq Num LSP Checksum LSP Holdtime   ATT/P/OL
1111.1111.1111.00-00 0x00000008  0x0B2C    827        1/0/0
1212.1212.1212.00-00* 0x00000007  0x1C1C    832        1/0/0
1212.1212.1212.01-00* 0x00000002  0xD237    427        0/0/0
1212.1212.1212.02-00* 0x00000002  0xA265    1118       0/0/0
1313.1313.1313.00-00 0x00000009  0xBCB1    830        1/0/0
1313.1313.1313.01-00 0x00000001  0x4840    0 (429)      0/0/0
1313.1313.1313.02-00 0x00000002  0xA853    1107       0/0/0
1313.1313.1313.03-00 0x00000002  0xA159    1131       0/0/0
1313.1313.1313.04-00 0x00000001  0x9C5E    440        0/0/0

IS-IS Level-2 Link State Database
LSPID         LSP Seq Num LSP Checksum LSP Holdtime   ATT/P/OL
1111.1111.1111.00-00 0x0000000C  0xDAD4    816        0/0/0
1111.2222.3333.00-00 0x00000006  0x352F    815        0/0/0
1212.1212.1212.00-00* 0x0000000A  0x6588    821        0/0/0
1212.1212.1212.01-00* 0x00000003  0x6031    1108       0/0/0
1313.1313.1313.00-00 0x0000000A  0xEA43    819        0/0/0
1313.1313.1313.01-00 0x00000002  0x4641    0 (432)      0/0/0
p1r2#

The following example output is from the p1r3 router:

p1r3#show isis database
IS-IS Level-1 Link State Database
LSPID         LSP Seq Num LSP Checksum LSP Holdtime   ATT/P/OL
1111.1111.1111.00-00 0x00000008  0x0B2C    819        1/0/0
1212.1212.1212.00-00 0x00000007  0x1C1C    822        1/0/0
1212.1212.1212.01-00 0x00000002  0xD237    415        0/0/0
1212.1212.1212.02-00 0x00000002  0xA265    1108       0/0/0
1313.1313.1313.00-00* 0x00000009  0xBCB1    824        1/0/0
1313.1313.1313.01-00* 0x00000001  0x4840    0 (421)      0/0/0
1313.1313.1313.02-00* 0x00000002  0xA853    1102       0/0/0
1313.1313.1313.03-00* 0x00000002  0xA159    1125       0/0/0
1313.1313.1313.04-00* 0x00000001  0x9C5E    434        0/0/0

IS-IS Level-2 Link State Database
LSPID         LSP Seq Num LSP Checksum LSP Holdtime   ATT/P/OL
1111.1111.1111.00-00 0x0000000C  0xDAD4    808        0/0/0
1111.2222.3333.00-00 0x00000006  0x352F    807        0/0/0
1212.1212.1212.00-00 0x0000000A  0x6588    811        0/0/0
1212.1212.1212.01-00 0x00000003  0x6031    1098       0/0/0
1313.1313.1313.00-00* 0x0000000A  0xEA43    813        0/0/0
1313.1313.1313.01-00* 0x00000002  0x4641    0 (420)      0/0/0
p1r3#

Yes, the Level 1 and Level 2 link-state database on all the routers in the pod is visible.

In the link-state database, which link-state packet (LSP) is identified with an asterisk?

The LSPs with an asterisk are the local LSPs—in other words, LSPs originated from this router.

Examine the routing table of the pxr2 and pxr3 routers within your pod. Do you see both the Level 1 and Level 2 routes?

The following example output is from the p1r2 router:

p1r2#show ip route
<output omitted>
Gateway of last resort is not set

   172.16.0.0/24 is subnetted, 2 subnets
i L2  172.16.10.0 [115/30] via 192.168.1.33, Serial1
          [115/30] via 192.168.1.17, Serial0
i L2  172.16.11.0 [115/30] via 192.168.1.33, Serial1
          [115/30] via 192.168.1.17, Serial0
   172.26.0.0/28 is subnetted, 3 subnets
i L1  172.26.1.48 [115/20] via 192.168.1.66, Ethernet0
i L1  172.26.1.32 [115/20] via 192.168.1.66, Ethernet0
i L1  172.26.1.16 [115/20] via 192.168.1.66, Ethernet0
   10.0.0.0/24 is subnetted, 1 subnets
i L1  10.1.1.0 [115/20] via 192.168.1.33, Serial1
         [115/20] via 192.168.1.17, Serial0
   192.168.1.0/28 is subnetted, 4 subnets
C    192.168.1.64 is directly connected, Ethernet0
C    192.168.1.32 is directly connected, Serial1
i L1  192.168.1.48 [115/20] via 192.168.1.33, Serial1
           [115/20] via 192.168.1.17, Serial0
           [115/20] via 192.168.1.66, Ethernet0
C    192.168.1.16 is directly connected, Serial0
C  192.168.101.0/24 is directly connected, Loopback10
p1r2#

The following example output is from the p1r3 router:

p1r3#show ip route
<output omitted>
Gateway of last resort is not set

   172.16.0.0/24 is subnetted, 2 subnets
i L2  172.16.10.0 [115/30] via 192.168.1.49, Serial0
i L2  172.16.11.0 [115/30] via 192.168.1.49, Serial0
   172.26.0.0/28 is subnetted, 3 subnets
C    172.26.1.48 is directly connected, Loopback13
C    172.26.1.32 is directly connected, Loopback12
C    172.26.1.16 is directly connected, Loopback11
   10.0.0.0/24 is subnetted, 1 subnets
i L1  10.1.1.0 [115/20] via 192.168.1.49, Serial0
   192.168.1.0/28 is subnetted, 4 subnets
C    192.168.1.64 is directly connected, Ethernet0
i L1  192.168.1.32 [115/20] via 192.168.1.65, Ethernet0
           [115/20] via 192.168.1.49, Serial0
C    192.168.1.48 is directly connected, Serial0
i L1  192.168.1.16 [115/20] via 192.168.1.65, Ethernet0
           [115/20] via 192.168.1.49, Serial0
i L1 192.168.101.0/24 [115/20] via 192.168.1.65, Ethernet0
p1r3#

Yes, both the Level 1 and Level 2 routes are in the p1r2 and p1r3 routing tables.

Step 3 Configure the pxr2 and pxr3 routers within your pod to be Level 1 IS-IS routers.

The following example configuration shows how to configure p1r2 and p1r3 to be Level 1 IS-IS routers:

p1r2(config)#router isis
p1r2(config-router)#is-type level-1

p1r3(config)#router isis
p1r3(config-router)#is-type level-1

NOTE

You will have to wait a minute or so after changing the IS type for the routing tables to converge.

Step 4 What are the advantages of configuring the pxr2 and pxr3 routers within your pod to be Level 1 IS-IS routers?

The advantages include having shorter routing tables in the Level 1 routers (containing only area routes and default route) and being less processor intensive.

Step 5 Re-examine the link-state database of the pxr2 and pxr3 routers within your pod. Do the pxr2 and pxr3 routers contain only the Level 1 link-state database now?

The following example output is from the p1r2 router:

p1r2#show isis database
IS-IS Level-1 Link State Database
LSPID         LSP Seq Num LSP Checksum LSP Holdtime   ATT/P/OL
1111.1111.1111.00-00 0x0000000D  0x0131    1117       1/0/0
1212.1212.1212.00-00* 0x0000000A  0x0C33    1111       0/0/0
1212.1212.1212.01-00* 0x00000005  0xCA3E    1125       0/0/0
1212.1212.1212.02-00* 0x00000002  0xA265    820        0/0/0
1313.1313.1313.00-00 0x0000000D  0xAAC9    1115       0/0/0
1313.1313.1313.01-00 0x00000001  0x4840    0 (131)      0/0/0
1313.1313.1313.02-00 0x00000002  0xA853    810        0/0/0
1313.1313.1313.03-00 0x00000002  0xA159    833        0/0/0
1313.1313.1313.04-00 0x00000002  0x9A5F    999        0/0/0
p1r2#

The following example output is from the p1r2 router:

p1r3#show isis database
IS-IS Level-1 Link State Database
LSPID         LSP Seq Num LSP Checksum LSP Holdtime   ATT/P/OL
1111.1111.1111.00-00 0x0000000D  0x0131    1109       1/0/0
1212.1212.1212.00-00 0x0000000A  0x0C33    1099       0/0/0
1212.1212.1212.01-00 0x00000005  0xCA3E    1114       0/0/0
1212.1212.1212.02-00 0x00000002  0xA265    809        0/0/0
1313.1313.1313.00-00* 0x0000000D  0xAAC9    1110       0/0/0
1313.1313.1313.01-00* 0x00000001  0x4840    0 (122)      0/0/0
1313.1313.1313.02-00* 0x00000002  0xA853    802        0/0/0
1313.1313.1313.03-00* 0x00000002  0xA159    826        0/0/0
1313.1313.1313.04-00* 0x00000002  0x9A5F    992        0/0/0
p1r3#

Yes, the pxr2 and pxr3 routers contain only the Level 1 link-state database now.

Step 6 Re-examine the routing table of the pxr2 and pxr3 routers now. What are the differences after they became Level 1–only IS-IS routers?

The following example output is from the p1r2 router:

p1r2#show ip route
<output omitted>
Gateway of last resort is 192.168.1.17 to network 0.0.0.0

   172.26.0.0/28 is subnetted, 3 subnets
i L1  172.26.1.48 [115/20] via 192.168.1.66, Ethernet0
i L1  172.26.1.32 [115/20] via 192.168.1.66, Ethernet0
i L1  172.26.1.16 [115/20] via 192.168.1.66, Ethernet0
   10.0.0.0/24 is subnetted, 1 subnets
i L1  10.1.1.0 [115/20] via 192.168.1.17, Serial0
         [115/20] via 192.168.1.33, Serial1
   192.168.1.0/28 is subnetted, 4 subnets
C    192.168.1.64 is directly connected, Ethernet0
C    192.168.1.32 is directly connected, Serial1
i L1  192.168.1.48 [115/20] via 192.168.1.17, Serial0
           [115/20] via 192.168.1.33, Serial1
           [115/20] via 192.168.1.66, Ethernet0
C    192.168.1.16 is directly connected, Serial0
C  192.168.101.0/24 is directly connected, Loopback10
i*L1 0.0.0.0/0 [115/10] via 192.168.1.17, Serial0
        [115/10] via 192.168.1.33, Serial1
p1r2#

The following example output is from the p1r3 router:

p1r3#show ip route
<output omitted>
Gateway of last resort is 192.168.1.49 to network 0.0.0.0

   172.26.0.0/28 is subnetted, 3 subnets
C    172.26.1.48 is directly connected, Loopback13
C    172.26.1.32 is directly connected, Loopback12
C    172.26.1.16 is directly connected, Loopback11
   10.0.0.0/24 is subnetted, 1 subnets
i L1  10.1.1.0 [115/20] via 192.168.1.49, Serial0
   192.168.1.0/28 is subnetted, 4 subnets
C    192.168.1.64 is directly connected, Ethernet0
i L1  192.168.1.32 [115/20] via 192.168.1.65, Ethernet0
           [115/20] via 192.168.1.49, Serial0
C    192.168.1.48 is directly connected, Serial0
i L1  192.168.1.16 [115/20] via 192.168.1.65, Ethernet0
           [115/20] via 192.168.1.49, Serial0
i L1 192.168.101.0/24 [115/20] via 192.168.1.65, Ethernet0
i*L1 0.0.0.0/0 [115/10] via 192.168.1.49, Serial0
p1r3#

The difference is that the routing tables are shorter, containing only area routes and a default route.

Step 7 In the pxr2 and pxr3 routing tables, do you see a default route through the pxr1 router?

Yes, a default route to the p1r1 router is visible.

Step 8 From the pxr2 or pxr3 routers, can you still ping the backbone_r1 router's loopback interfaces?

Yes, as shown in the following example output, the p1r2 and p1r3 routers can still ping the backbone_r1 router's loopback interfaces:

p1r2#ping 172.16.10.100

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 172.16.10.100, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 56/74/136 ms
p1r2#ping 172.16.11.100

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 172.16.11.100, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 56/56/60 ms
p1r2#

p1r3#ping 172.16.10.100

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 172.16.10.100, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 56/89/216 ms
p1r3#ping 172.16.11.100

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 172.16.11.100, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 60/60/60 ms
p1r3#

Step 9 Save the current configurations of all the routers within your pod to NVRAM.

The following example shows how to save the configuration of the p1r1 router using the copy run start command (this is an abbreviated form of the copy running-config startup-config command):

p1r1#copy run start
Destination filename [startup-config]?
Building configuration...
p1r1#

Answers to Task 4: Configure Route Summarization

Complete the following steps:

Step 1 From pxr3, telnet to the backbone_r1 router using the password cisco.

The following example output is from the p1r3 router:

p1r3#bbr1
Trying bbr1 (10.1.1.100)... Open


User Access Verification

Password:
backbone_r1>

Step 2 Display the routing table of the backbone_r1 router. Do you see your 192.168.x.y/28 and 172.26.x.y/28 subnets?

The following example output is from the backbone_r1 router:

backbone_r1>show ip route
<output omitted>
Gateway of last resort is not set

   172.16.0.0/24 is subnetted, 2 subnets
C    172.16.10.0 is directly connected, Loopback100
C    172.16.11.0 is directly connected, Loopback101
   172.26.0.0/28 is subnetted, 3 subnets
i L2  172.26.1.48 [115/30] via 10.1.1.1, Serial0/0
i L2  172.26.1.32 [115/30] via 10.1.1.1, Serial0/0
i L2  172.26.1.16 [115/30] via 10.1.1.1, Serial0/0
   10.0.0.0/24 is subnetted, 1 subnets
C    10.1.1.0 is directly connected, Serial0/0
   192.168.1.0/28 is subnetted, 4 subnets
i L2  192.168.1.64 [115/30] via 10.1.1.1, Serial0/0
i L2  192.168.1.32 [115/20] via 10.1.1.1, Serial0/0
i L2  192.168.1.48 [115/20] via 10.1.1.1, Serial0/0
i L2  192.168.1.16 [115/20] via 10.1.1.1, Serial0/0
i L2 192.168.101.0/24 [115/30] via 10.1.1.1, Serial0/0
backbone_r1>

Yes, the 192.168.1.y/28 and 172.26.1.y/28 subnets appear in the backbone_r1 router's routing table.

Step 3 Exit the telnet to the backbone_r1 router.

The following example output is from the backbone_r1 router:

backbone_r1>exit

[Connection to bbr1 closed by foreign host]
p1r3#

Step 4 Configure the Level 1–2 router within your pod to perform route summarization. Summarize the 192.168.x.y/28 and 172.26.x.y/28 subnets within your pod to 192.168.x.0/24 and 172.26.x.0/24 (where x is your pod number).

The following example shows how to configure the p1r1 router, the Level 1–2 router in pod 1, to perform route summarization:

p1r1(config)#router isis
p1r1(config-router)#summary-address 192.168.1.0 255.255.255.0
p1r1(config-router)#summary-address 172.26.1.0 255.255.255.0

Step 5 Telnet to the backbone_r1 router.

The following example output is from the p1r1 router:

p1r1#bbr1
Trying bbr1 (10.1.1.100)... Open


User Access Verification

Password:
backbone_r1>

Step 6 Re-examine the routing table of the backbone_r1 router. Do you see your summarized routes?

The following example output is from the backbone_r1 router:

backbone_r1>show ip route
<output omitted>
Gateway of last resort is not set

   172.16.0.0/24 is subnetted, 2 subnets
C    172.16.10.0 is directly connected, Loopback100
C    172.16.11.0 is directly connected, Loopback101
   172.26.0.0/24 is subnetted, 1 subnets
i L2  172.26.1.0 [115/30] via 10.1.1.1, Serial0/0
   10.0.0.0/24 is subnetted, 1 subnets
C    10.1.1.0 is directly connected, Serial0/0
i L2 192.168.1.0/24 [115/20] via 10.1.1.1, Serial0/0
i L2 192.168.101.0/24 [115/30] via 10.1.1.1, Serial0/0
backbone_r1>

Yes, the summarized routes to 172.26.1.0 and 192.168.1.0 are in the backbone_r1 router's routing table.

Step 7 From the backbone_r1 router, can you ping all the interfaces within your pod?

Yes, as the example output shows, the backbone_r1 router can ping all the interfaces on the pod 1 routers:

backbone_r1>ping 192.168.1.17

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 192.168.1.17, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 36/64/172 ms
backbone_r1>ping 192.168.1.18

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 192.168.1.18, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 64/69/84 ms
backbone_r1>ping 192.168.1.33

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 192.168.1.33, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 36/40/56 ms
backbone_r1>ping 192.168.1.34

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 192.168.1.34, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 64/68/84 ms
backbone_r1>ping 192.168.1.49

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 192.168.1.49, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 36/40/56 ms
backbone_r1>ping 192.168.1.50

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 192.168.1.50, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 64/68/84 ms
backbone_r1>ping 192.168.1.65

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 192.168.1.65, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 64/69/84 ms
backbone_r1>ping 192.168.1.66

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 192.168.1.66, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 64/67/80 ms
backbone_r1>ping 192.168.101.101

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 192.168.101.101, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 64/69/88 ms
backbone_r1>ping 172.26.1.17

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 172.26.1.17, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 64/106/268 ms
backbone_r1>ping 172.26.1.33

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 172.26.1.33, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 64/69/84 ms
backbone_r1>ping 172.26.1.49

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 172.26.1.49, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 64/68/84 ms
backbone_r1>

Step 8 Exit the telnet to the backbone_r1 router.

The following example output is from the backbone_r1 router:

backbone_r1>
backbone_r1>exit

[Connection to bbr1 closed by foreign host]
p1r1#

Step 9 Save the current configurations of all the routers within your pod to NVRAM.

The following example shows how to save the configuration of the p1r1 router using the copy run start command (this is an abbreviated form of the copy running-config startup-config command):

p1r1#copy run start
Destination filename [startup-config]?
Building configuration...
p1r1#

Answers to Task 5: Using IS-IS show and debug Commands

Complete the following steps:

Step 1 At the pxr2 router, enable the debug isis adj-packets command and observe the debug output.

The following example shows enabling the debug on the p1r2 router and the output that results:

p1r2#debug isis adj-packets
IS-IS Adjacency related packets debugging is on
p1r2#
01:45:23: ISIS-Adj: Sending serial IIH on Serial1
01:45:23: ISIS-Adj: Rec serial IIH from *HDLC* (Serial1), cir type L1L2, cir id
01
01:45:23: ISIS-Adj: rcvd state UP, old state UP, new state UP
01:45:23: ISIS-Adj: Action = ACCEPT
01:45:24: ISIS-Adj: Sending L1 IIH on Loopback10
p1r2#
01:45:24: ISIS-Adj: Sending L1 IIH on Ethernet0
p1r2#
01:45:26: ISIS-Adj: Rec serial IIH from *HDLC* (Serial0), cir type L1L2, cir id
00
01:45:26: ISIS-Adj: rcvd state UP, old state UP, new state UP
01:45:26: ISIS-Adj: Action = ACCEPT
01:45:27: ISIS-Adj: Sending L1 IIH on Loopback10
p1r2#
01:45:27: ISIS-Adj: Sending L1 IIH on Ethernet0
01:45:28: ISIS-Adj: Sending serial IIH on Serial0
p1r2#
01:45:30: ISIS-Adj: Sending L1 IIH on Loopback10
01:45:30: ISIS-Adj: Sending L1 IIH on Ethernet0
01:45:31: ISIS-Adj: Rec L1 IIH from 0010.7b81.d6ec (Ethernet0), cir type L1, cir
 id 1212.1212.1212.01
p1r2#

What type of hello is pxr2 sending to pxr3 over the Ethernet interface?

The p1r2 router is sending an L1 hello to the p1r3 router.

Step 2 Shut the pxr2 E0 interface and observe the debug output.

The following example shows shutting down the Ethernet 0 interface on the p1r2 router and the output that results:

p1r2#conf t
Enter configuration commands, one per line. End with CNTL/Z.
01:45:38: ISIS-Adj: Rec L1 IIH from 0010.7b81.d6ec (Ethernet0), cir type L1,
  cir
 id 1212.1212.1212.01
01:45:39: ISIS-Adj: Sending L1 IIH on Loopback10
01:45:39: ISIS-Adj: Sending L1 IIH on Ethernet0
01:45:39: ISIS-Adj: Sending serial IIH on Serial1
p1r2(config)#int e0
01:45:41: ISIS-Adj: Rec serial IIH from *HDLC* (Serial1), cir type L1L2,
  cir id
01
01:45:41: ISIS-Adj: rcvd state UP, old state UP, new state UP
01:45:41: ISIS-Adj: Action = ACCEPT
01:45:42: ISIS-Adj: Sending L1 IIH on Loopback10
01:45:42: ISIS-Adj: Sending L1 IIH on Ethernet0
p1r2(config-if)#shutdown
p1r2(config-if)#
01:45:45: ISIS-Adj: Sending serial IIH on Serial0
01:45:45: ISIS-Adj: Sending L1 IIH on Loopback10
01:45:45: ISIS-Adj: Rec serial IIH from *HDLC* (Serial0), cir type L1L2,
  cir id
00
01:45:45: ISIS-Adj: rcvd state UP, old state UP, new state UP
01:45:45: ISIS-Adj: Action = ACCEPT
01:45:46: %LINK-5-CHANGED: Interface Ethernet0, changed state to
  administratively down
01:45:47: %LINEPROTO-5-UPDOWN: Line protocol on Interface Ethernet0,
  changed state to down
01:45:48: ISIS-Adj: Sending L1 IIH on Loopback10
01:45:48: ISIS-Adj: Sending serial IIH on Serial1
01:45:49: ISIS-Adj: Rec serial IIH from *HDLC* (Serial1), cir type L1L2,
  cir id01
01:45:49: ISIS-Adj: rcvd state UP, old state UP, new state UP
01:45:49: ISIS-Adj: Action = ACCEPT
01:45:50: ISIS-Adj: Sending L1 IIH on Loopback10
01:45:53: ISIS-Adj: Sending L1 IIH on Loopback10
01:45:54: ISIS-Adj: Sending serial IIH on Serial0
01:45:54: ISIS-Adj: Rec serial IIH from *HDLC* (Serial0), cir type L1L2,
  cir id00
01:45:54: ISIS-Adj: rcvd state UP, old state UP, new state UP
01:45:54: ISIS-Adj: Action = ACCEPT
01:45:56: ISIS-Adj: Sending serial IIH on Serial1
01:45:56: ISIS-Adj: Sending L1 IIH on Loopback10
01:45:58: ISIS-Adj: Rec serial IIH from *HDLC* (Serial1), cir type L1L2,
  cir id01
01:45:58: ISIS-Adj: rcvd state UP, old state UP, new state UP
01:45:58: ISIS-Adj: Action = ACCEPT
p1r2(config-if)#

Step 3 No shut the pxr2 E0 interface and observe the debug output. From the debug output, determine which router (pxr2 or pxr3) is elected as the DR.

NOTE

The correct term in IS-IS is DIS, not DR. However, the debug output on the router uses the term DR, so we will also use the term DR in this task.

In the debug output, you should see something similar to the output shown in Example S-32 if pxr3 is the DR.

Example S-32 debug isis adj-packets Command Output from Router pxr2 If Router pxr3 Is the DR

02:23:12: ISIS-Adj: Adjacency state goes to Up
02:23:12: ISIS-Adj: Run level 1 DR election for Ethernet0
02:23:12: ISIS-Adj: New level 1 DR 3333.3333.3333 on Ethernet0
 pxr2#

Or, in the debug output, you should see something similar to the output shown in Example S-33 if pxr2 is the DR.

Example S-33 debug isis adj-packets Command Output from Router pxr2 If Router pxr2 Is the DR

05:19:43: ISIS-Adj: Run level 1 DR election for Ethernet0
05:19:43: ISIS-Adj: No change (it's us)
 pxr2#

What determines who will be elected as the DR on the Ethernet?

The following example shows no shutting the Ethernet 0 interface on the p1r2 router and the output that results:

p1r2(config-if)#int e0
01:46:17: ISIS-Adj: Sending L1 IIH on Loopback10
01:46:17: ISIS-Adj: Sending serial IIH on Serial0
p1r2(config-if)#no shutdown
p1r2(config-if)#
01:46:20: ISIS-Adj: Sending L1 IIH on Loopback10
01:46:21: ISIS-Adj: Sending L1 IIH on Ethernet0
01:46:21: ISIS-Adj: Rec L1 IIH from 0010.7b81.d6ec (Ethernet0), cir type L1,
  cir id 1212.1212.1212.01
01:46:21: ISIS-Adj: New adjacency, level 1 for 0010.7b81.d6ec
01:46:22: ISIS-Adj: Sending L1 IIH on Ethernet0
01:46:22: %LINK-3-UPDOWN: Interface Ethernet0, changed state to up
01:46:22: ISIS-Adj: Sending serial IIH on Serial1
01:46:23: ISIS-Adj: Rec serial IIH from *HDLC* (Serial0), cir type L1L2,
  cir id

00
01:46:23: ISIS-Adj: rcvd state UP, old state UP, new state UP
01:46:23: ISIS-Adj: Action = ACCEPT
01:46:23: %LINEPROTO-5-UPDOWN: Line protocol on Interface Ethernet0,
  changed state to up
01:46:23: ISIS-Adj: Sending L1 IIH on Loopback10
01:46:24: ISIS-Adj: Sending L1 IIH on Ethernet0
01:46:24: ISIS-Adj: Rec serial IIH from *HDLC* (Serial1), cir type L1L2,
  cir id
01
01:46:24: ISIS-Adj: rcvd state UP, old state UP, new state UP
01:46:24: ISIS-Adj: Action = ACCEPT
01:46:26: ISIS-Adj: Sending serial IIH on Serial0
01:46:26: ISIS-Adj: Sending L1 IIH on Loopback10
01:46:27: ISIS-Adj: Sending L1 IIH on Ethernet0
01:46:29: ISIS-Adj: Sending L1 IIH on Loopback10
01:46:29: ISIS-Adj: Rec L1 IIH from 0010.7b81.d6ec (Ethernet0), cir type L1,
  cir
 id 1212.1212.1212.01
01:46:29: ISIS-Adj: Adjacency state goes to Up
01:46:29: ISIS-Adj: Run level 1 DR election for Ethernet0
01:46:29: ISIS-Adj: No change (it's us)
01:46:30: ISIS-Adj: Sending L1 IIH on Ethernet0
01:46:30: ISIS-Adj: Rec serial IIH from *HDLC* (Serial0), cir type L1L2, cir id
00
01:46:30: ISIS-Adj: rcvd state UP, old state UP, new state UP
01:46:30: ISIS-Adj: Action = ACCEPT
01:46:32: ISIS-Adj: Sending serial IIH on Serial1
01:46:32: ISIS-Adj: Sending L1 IIH on Loopback10
01:46:32: ISIS-Adj: Rec serial IIH from *HDLC* (Serial1), cir type L1L2, cir id
01
01:46:32: ISIS-Adj: rcvd state UP, old state UP, new state UP
01:46:32: ISIS-Adj: Action = ACCEPT
01:46:33: ISIS-Adj: Sending L1 IIH on Ethernet0
01:46:35: ISIS-Adj: Sending L1 IIH on Loopback10
01:46:35: ISIS-Adj: Sending serial IIH on Serial0
01:46:36: ISIS-Adj: Sending L1 IIH on Ethernet0
p1r2(config-if)#^Z
p1r2#
01:46:38: ISIS-Adj: Sending L1 IIH on Loopback10
01:46:38: ISIS-Adj: Rec L1 IIH from 0010.7b81.d6ec (Ethernet0), cir type L1,
  cir
 id 1212.1212.1212.01
01:46:39: %SYS-5-CONFIG_I: Configured from console by console
01:46:39: ISIS-Adj: Sending serial IIH on Serial1
01:46:39: ISIS-Adj: Sending L1 IIH on Ethernet0
01:46:40: ISIS-Adj: Rec serial IIH from *HDLC* (Serial0), cir type L1L2,
  cir id00
01:46:40: ISIS-Adj: rcvd state UP, old state UP, new state UP
01:46:40: ISIS-Adj: Action = ACCEPT
01:46:40: ISIS-Adj: Rec serial IIH from *HDLC* (Serial1), cir type L1L2,
  cir id01
01:46:40: ISIS-Adj: rcvd state UP, old state UP, new state UP
01:46:40: ISIS-Adj: Action = ACCEPT
01:46:41: ISIS-Adj: Sending L1 IIH on Loopback10

As the example output shows, p1r2 remains the DR. Priority determines who is the DR. The default is 64; a priority of 0 means that the router cannot be elected. If two routers have the same priority, the one with the highest MAC address is the DR.

Step 4 Disable debug isis adj-packets at the pxr2 router.

The following example shows how to disable debugging on the p1r2 router:

p1r2#no debug all
All possible debugging has been turned off
p1r2#
01:46:42: ISIS-Adj: Sending L1 IIH on Ethernet0
p1r2#

Step 5 At the DR (as determined from Step 3), enter the show clns int e0 command. What is the default IS-IS router priority set to?

The following example shows the output of the show clns int 0 command on the DR, p1r2:

p1r2#show clns int e0
Ethernet0 is up, line protocol is up
 Checksums enabled, MTU 1497, Encapsulation SAP
 ERPDUs enabled, min. interval 10 msec.
 RDPDUs enabled, min. interval 100 msec., Addr Mask enabled
 Congestion Experienced bit set at 4 packets
 CLNS fast switching enabled
 CLNS SSE switching disabled
 DEC compatibility mode OFF for this interface
 Next ESH/ISH in 30 seconds
 Routing Protocol: IS-IS
  Circuit Type: level-1-2
  Interface number 0x2, local circuit ID 0x1
  Level-1 Metric: 10, Priority: 64, Circuit ID: 1212.1212.1212.01
  Number of active level-1 adjacencies: 1
  Next IS-IS LAN Level-1 Hello in 420 milliseconds
p1r2#

As shown, the default router priority is set to 64.

Step 6 At the DR (as determined from Step 3), change the E0 interface IS-IS router priority to 63.

The following example shows how to change the IS-IS router priority on the E0 interface of p1r2, the DR:

p1r2(config)#int e0
p1r2(config-if)#isis priority 63

Step 7 At the DR (as determined from Step 3), enter the show clns int e0 command again and verify that the DR is now changed to the other router.

The Circuit ID field in the show clns int e0 output identifies which router is the DR. Example S-34 shows the output of this command on the pxr3 router. In this example, the DR is the pxr2 router and the pxr3 router has an IS-IS priority of 63.

Example S-34 show clns Command Output from Router pxr3 If Router pxr2 Is the DR

pxr3#show clns int e0
Ethernet0 is up, line protocol is up
 Checksums enabled, MTU 1497, Encapsulation SAP
 ERPDUs enabled, min. interval 10 msec.
 RDPDUs enabled, min. interval 100 msec., Addr Mask enabled
 Congestion Experienced bit set at 4 packets
 CLNS fast switching enabled
 CLNS SSE switching disabled
 DEC compatibility mode OFF for this interface
 Next ESH/ISH in 21 seconds
 Routing Protocol: IS-IS
  Circuit Type: level-1-2
  Interface number 0x1, local circuit ID 0x1
  Level-1 Metric: 10, Priority: 63, Circuit ID: 2222.2222.2222.01
  Number of active level-1 adjacencies: 1
Next IS-IS LAN Level-1 HELLO in 8 seconds

The following example is the output of the show clns int e0 command on the p1r2 router, the DR:

p1r2#show clns int e0
Ethernet0 is up, line protocol is up
 Checksums enabled, MTU 1497, Encapsulation SAP
 ERPDUs enabled, min. interval 10 msec.
 RDPDUs enabled, min. interval 100 msec., Addr Mask enabled
 Congestion Experienced bit set at 4 packets
 CLNS fast switching enabled
 CLNS SSE switching disabled
 DEC compatibility mode OFF for this interface
 Next ESH/ISH in 24 seconds
 Routing Protocol: IS-IS
  Circuit Type: level-1-2
  Interface number 0x2, local circuit ID 0x1
  Level-1 Metric: 10, Priority: 63, Circuit ID: 1313.1313.1313.01
  Number of active level-1 adjacencies: 1
  Next IS-IS LAN Level-1 Hello in 4 seconds
p1r2#

In this example, the priority is now 63 on interface E0. The circuit ID is that of router p1r3, indicating that p1r3 is now the DR.

Step 8 At the pxr2 router, enable the debug isis update-packets command. Shut and no shut the E0 interface on the pxr2 router and observe the debug output.

The following example shows how to enable the debug on the p1r2 router and the output on the router:

p1r2#debug isis update-packets
IS-IS Update related packet debugging is on
p1r2#
01:58:08: ISIS-SNP: Rec L1 CSNP from 1313.1313.1313 (Ethernet0)
p1r2#conf t
Enter configuration commands, one per line. End with CNTL/Z.
p1r2(config)#int e0
p1r2(config-if)#shutdown
p1r2(config-if)#
01:58:16: ISIS-SNP: Rec L1 CSNP from 1313.1313.1313 (Ethernet0)
01:58:16: ISIS-Update: Building L1 LSP
01:58:16: ISIS-Update: TLV contents different, code 80
01:58:16: ISIS-Update: TLV contents different, code 2
01:58:16: ISIS-Update: Full SPF required
01:58:16: ISIS-Update: Building L1 pseudonode LSP for Ethernet0
01:58:16: ISIS-Update: TLV contents different, code 2
01:58:16: ISIS-Update: Full SPF required
01:58:16: ISIS-Update: Sending L1 LSP 1212.1212.1212.00-00, seq 10,
  ht 1199 on Serial1
01:58:16: ISIS-Update: Sending L1 LSP 1212.1212.1212.00-00, seq 10,
  ht 1199 on Serial0
01:58:16: ISIS-Update: Sending L1 LSP 1212.1212.1212.01-00, seq 9,
  ht 1199 on Serial1
01:58:16: ISIS-Update: Sending L1 LSP 1212.1212.1212.01-00, seq 9,
  ht 1199 on Serial0
01:58:17: ISIS-SNP: Rec L1 PSNP from 1111.1111.1111 (Serial1)
01:58:17: ISIS-SNP: PSNP entry 1212.1212.1212.00-00, seq 10, ht 1196
01:58:17: ISIS-SNP: PSNP entry 1212.1212.1212.01-00, seq 9, ht 1197
01:58:17: ISIS-SNP: Rec L1 PSNP from 1111.1111.1111 (Serial0)
01:58:17: ISIS-SNP: PSNP entry 1212.1212.1212.00-00, seq 10, ht 1196
01:58:17: ISIS-SNP: PSNP entry 1212.1212.1212.01-00, seq 9, ht 1197
01:58:18: %LINK-5-CHANGED: Interface Ethernet0, changed state to
  administratively down
01:58:18: ISIS-Update: Building L1 LSP
01:58:18: ISIS-Update: No change, suppress L1 LSP 1212.1212.1212.00-00, seq 11
01:58:19: %LINEPROTO-5-UPDOWN: Line protocol on Interface Ethernet0,
  changed state to down
p1r2(config-if)#no shutdown
p1r2(config-if)#
01:58:30: ISIS-Update: Building L1 LSP
01:58:30: ISIS-Update: TLV contents different, code 80
01:58:30: ISIS-Update: Leaf routes changed
01:58:30: ISIS-Update: Building L1 pseudonode LSP for Ethernet0
01:58:30: ISIS-Update: No change, suppress L1 LSP 1212.1212.1212.01-00, seq A
01:58:30: ISIS-Update: Sending L1 LSP 1212.1212.1212.00-00, seq 11,
  ht 1199 on Serial1
01:58:30: ISIS-Update: Sending L1 LSP 1212.1212.1212.00-00, seq 11,
  ht 1199 on Serial0
01:58:30: ISIS-Update: Rec L1 LSP 1313.1313.1313.01-00, seq 2, ht 1197,
01:58:30: ISIS-Update: from SNPA *HDLC* (Serial1)
01:58:30: ISIS-Update: LSP newer than database copy
01:58:30: ISIS-Update: TLV contents different, code 2
01:58:30: ISIS-Update: Full SPF required
01:58:31: ISIS-Update: Building L1 LSP
01:58:31: ISIS-Update: No change, suppress L1 LSP 1212.1212.1212.00-00, seq 12
01:58:31: ISIS-SNP: Rec L1 PSNP from 1111.1111.1111 (Serial1)
01:58:31: ISIS-SNP: PSNP entry 1212.1212.1212.00-00, seq 11, ht 1197
01:58:31: ISIS-SNP: Rec L1 PSNP from 1111.1111.1111 (Serial0)
01:58:31: ISIS-SNP: PSNP entry 1212.1212.1212.00-00, seq 11, ht 1196
01:58:31: ISIS-Update: Build L1 PSNP entry for 1313.1313.1313.01-00, seq 2
01:58:31: ISIS-Update: Sending L1 PSNP on Serial1
01:58:31: ISIS-Update: Build L1 PSNP entry for 1313.1313.1313.01-00, seq 2
01:58:31: ISIS-Update: Sending L1 PSNP on Serial0
01:58:32: %LINK-3-UPDOWN: Interface Ethernet0, changed state to up
01:58:33: %LINEPROTO-5-UPDOWN: Line protocol on Interface Ethernet0,
  changed state to up
01:58:35: ISIS-Update: Purging LSP 1212.1212.1212.01-00, seq 9
01:58:35: ISIS-Update: Building L1 LSP
01:58:35: ISIS-Update: Rate limiting L1 LSP 1212.1212.1212.00-00, seq 12
01:58:35: ISIS-Update: TLV contents different, code 2
01:58:35: ISIS-Update: Full SPF required
01:58:35: ISIS-Update: Sending L1 LSP 1212.1212.1212.01-00, seq 9,
  ht 0 on Ethernet0
01:58:35: ISIS-Update: Sending L1 LSP 1212.1212.1212.01-00, seq 9,
  ht 0 on Serial1
01:58:35: ISIS-Update: Sending L1 LSP 1212.1212.1212.01-00, seq 9,
  ht 0 on Serial0
01:58:35: ISIS-Update: Rec L1 LSP 1212.1212.1212.01-00, seq 9, ht 0,
01:58:35: ISIS-Update: from SNPA 0010.7b81.d6ec (Ethernet0)
01:58:35: ISIS-Update: LSP same as database copy
01:58:35: ISIS-Update: Rec L1 LSP 1212.1212.1212.01-00, seq 9, ht 0,
01:58:35: ISIS-Update: from SNPA *HDLC* (Serial1)
01:58:35: ISIS-Update: LSP same as database copy
01:58:35: ISIS-Update: Sending L1 LSP 1212.1212.1212.00-00, seq 12,
  ht 1199 on Ethernet0
01:58:35: ISIS-Update: Sending L1 LSP 1212.1212.1212.00-00, seq 12,
  ht 1199 on Serial1
01:58:35: ISIS-Update: Sending L1 LSP 1212.1212.1212.00-00, seq 12,
  ht 1199 on Serial0
01:58:35: ISIS-Update: Rec L1 LSP 1313.1313.1313.01-00, seq 3, ht 1196,
01:58:35: ISIS-Update: from SNPA 0010.7b81.d6ec (Ethernet0)
01:58:35: ISIS-Update: LSP newer than database copy
01:58:35: ISIS-Update: TLV contents different, code 2
01:58:35: ISIS-Update: Full SPF required
01:58:35: ISIS-Update: Sending L1 LSP 1313.1313.1313.01-00, seq 3,
  ht 1194 on Serial1
01:58:35: ISIS-Update: Sending L1 LSP 1313.1313.1313.01-00, seq 3,
  ht 1194 on Serial0
01:58:36: ISIS-SNP: Rec L1 PSNP from 1111.1111.1111 (Serial0)
01:58:36: ISIS-SNP: PSNP entry 1212.1212.1212.00-00, seq 12, ht 1197
01:58:36: ISIS-SNP: PSNP entry 1212.1212.1212.01-00, seq 9, ht 0
01:58:36: ISIS-SNP: PSNP entry 1313.1313.1313.01-00, seq 3, ht 1192
01:58:36: ISIS-Update: Build L1 PSNP entry for 1212.1212.1212.01-00, seq 9
01:58:36: ISIS-Update: Sending L1 PSNP on Serial1
01:58:36: ISIS-SNP: Rec L1 PSNP from 1111.1111.1111 (Serial1)
01:58:36: ISIS-SNP: PSNP entry 1212.1212.1212.00-00, seq 12, ht 1197
01:58:36: ISIS-SNP: PSNP entry 1313.1313.1313.01-00, seq 3, ht 1192
01:58:41: ISIS-SNP: Rec L1 CSNP from 1313.1313.1313 (Ethernet0)
p1r2(config-if)#exit
p1r2(config)#
01:58:50: ISIS-SNP: Rec L1 CSNP from 1313.1313.1313 (Ethernet0)

Step 9 Disable the debug isis update-packets at the pxr2 router.

The following example shows how to disable the debug on the p1r2 router:

p1r2#no debug all
All possible debugging has been turned off

Step 10 At the pxr2 router, use the proper show command to verify how often and why the router has run a full SPF calculation.

The following example shows the output of the show isis spf-log command on the p1r2 router:

p1r2#show isis spf-log

  Level 1 SPF log
 When  Duration Nodes Count   Last trigger LSP  Triggers
00:46:50   12   5   2 1313.1313.1313.02-00 NEWLSP
00:46:45   16   7   3 1313.1313.1313.03-00 NEWLSP TLVCONTENT
00:46:40   16   8   2 1313.1313.1313.04-00 NEWLSP TLVCONTENT
00:40:10   16   8   4 1313.1313.1313.00-00 ATTACHFLAG LSPHEADER
00:36:15   16   8   1            PERIODIC
00:31:28    8   3   5 1212.1212.1212.01-00 NEWLEVEL DELADJ LSPHEADER
00:30:37   40   8   2 1212.1212.1212.00-00 NEWADJ TLVCONTENT
00:30:32   36   4   3 1313.1313.1313.00-00 NEWADJ TLVCONTENT
00:30:22   20   8   1 1111.1111.1111.00-00 TLVCONTENT
00:30:17   24   8   3 1313.1313.1313.00-00 NEWADJ LSPHEADER TLVCONTEN
T
00:21:16   16   8   1            PERIODIC
00:14:29   20   8   3 1212.1212.1212.01-00 IPBACKUP IPQUERY TLVCONTEN
T
00:14:24   16   8   1 1313.1313.1313.00-00 TLVCONTENT
00:13:51   16   8   1 1313.1313.1313.00-00 TLVCONTENT
00:13:47   24   8   2 1212.1212.1212.01-00 NEWADJ TLVCONTENT
00:06:16   16   8   1            PERIODIC
00:04:27   16   8   4 1313.1313.1313.01-00 NEWLSP TLVCONTENT
00:01:58   20   9   3 1212.1212.1212.01-00 IPQUERY TLVCONTENT
00:01:43   24   8   4 1313.1313.1313.01-00 NEWADJ TLVCONTENT
p1r2#

Step 11 At the pxr2 router, use the proper show command to examine the IS-IS neighbor table. How many entries do you see? Are they all Level 1 adjacency?

The following example shows the output of the show clns is-neighbors command on the p1r2 router:

p1r2#show clns is-neighbors

System Id   Interface  State Type Priority Circuit Id     Format
1111.1111.1111 Se1     Up   L1  0     01       Phase V
1111.1111.1111 Se0     Up   L1  0     00       Phase V
1313.1313.1313 Et0     Up   L1  64    1313.1313.1313.0Phase V
p1r2#

There are three entries; all are Level 1.

Step 12 At the pxr1 router, use the proper show command to examine the IS-IS neighbor table. How many entries do you see? Do you see both Level 2 and Level 1 adjacency?

The following example shows the output of the show clns is-neighbors command on the p1r1 router:

p1r1#show clns is-neighbors

System Id   Interface  State Type Priority Circuit Id     Format
1212.1212.1212 Se1     Up   L1  0     01       Phase V
1212.1212.1212 Se0     Up   L1  0     00       Phase V
1313.1313.1313 Se2     Up   L1  0     00       Phase V
1111.2222.3333 Se3     Up   L2  0     00       Phase V
p1r1#

There are four entries. The adjacencies to the other routers in pod 1 are Level 1, and the adjacency to the backbone_r1 router is Level 2.

Step 13 Display the running configuration of the pxr1 router. Is clns routing enabled by default?

The following example output is from the p1r1 router. The clns routing command is on by default:

p1r1#show run
Building configuration...

Current configuration:
!
version 12.0
service timestamps debug uptime
service timestamps log uptime
no service password-encryption
!
hostname p1r1
!
enable secret 5 $1$dlQh$WrD8xeBBJLywzPs6AMZUO/
enable password sanfran
!
ip subnet-zero
no ip domain-lookup
ip host p1r1 192.168.1.17 192.168.1.33 192.168.1.49 10.1.1.1
ip host p1r2 192.168.1.65 192.168.1.18 192.168.1.34
ip host p1r3 192.168.1.66 192.168.1.50
ip host bbr1 10.1.1.100
clns routing
!
!
!
interface Ethernet0
 no ip address
 no ip directed-broadcast
 shutdown
!
interface Serial0
 bandwidth 64
 ip address 192.168.1.17 255.255.255.240
 no ip directed-broadcast
 ip router isis
 no ip mroute-cache
 no fair-queue
 clockrate 64000
!
interface Serial1
 bandwidth 64
 ip address 192.168.1.33 255.255.255.240
 no ip directed-broadcast
 ip router isis
 clockrate 64000
!
interface Serial2
 bandwidth 64
 ip address 192.168.1.49 255.255.255.240
 no ip directed-broadcast
 ip router isis
 clockrate 64000
!
interface Serial3
 bandwidth 64
 ip address 10.1.1.1 255.255.255.0
 no ip directed-broadcast
 ip router isis
!
interface BRI0
 no ip address
 no ip directed-broadcast
 shutdown
!
router isis
 summary-address 192.168.1.0 255.255.255.0
 summary-address 172.26.1.0 255.255.255.0
 net 00.0001.1111.1111.1111.00
!
ip classless
!
!
!
line con 0
 exec-timeout 0 0
 logging synchronous
 transport input none
line aux 0
line vty 0 4
 password cisco
 login
!
end

p1r1#

Step 14 Save the current configurations of all the routers within your pod to NVRAM.

The following example shows how to save the configuration of the p1r1 router using the copy run start command (this is an abbreviated form of the copy running-config startup-config command):

p1r1#copy run start
Destination filename [startup-config]?
Building configuration...
p1r1#

NOTE

If you go on to do the Configuration Exercises in Chapter 5, "Configuring EIGRP," of the Cisco Press book Building Scalable Cisco Networks, you will need to change setup Step 2 to

Step 2 Disable IS-IS on all the routers within your pod.

Return to Beginning Previous Section

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Last Update: November 17, 2020

Email Address

Configuring IS-IS Protocol

Chapter Information

Contents

Chapter Description

From the Book

Answers to Configuration Exercise: Configuring a Multiarea IS-IS Network

Answers to Setup

Answers to Task 1: Enabling IS-IS Within Your Pod

Answers to Task 2: Enabling Connectivity to the backbone_r1 Router

Answers to Task 3: Changing the IS-IS Router Type

Answers to Task 4: Configure Route Summarization

Answers to Task 5: Using IS-IS show and debug Commands

Example S-32 debug isis adj-packets Command Output from Router pxr2 If Router pxr3 Is the DR

Example S-33 debug isis adj-packets Command Output from Router pxr2 If Router pxr2 Is the DR

Example S-34 show clns Command Output from Router pxr3 If Router pxr2 Is the DR

Cisco Press Promotional Mailings & Special Offers

Overview

Collection and Use of Information

Questions and Inquiries

Online Store

Surveys

Contests and Drawings

Newsletters

Service Announcements

Customer Service

Other Collection and Use of Information

Application and System Logs

Web Analytics

Cookies and Related Technologies

Do Not Track

Security

Children

Marketing

Correcting/Updating Personal Information

Choice/Opt-out

Sale of Personal Information

Supplemental Privacy Statement for California Residents

Sharing and Disclosure

Links

Requests and Contact

Changes to this Privacy Notice