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Cisco OSPF Route Redistribution

Configuration Example 3: Redistributing Classful Routes into OSPF as Type 1 Routes Using a Specific Metric

Routes are redistributed in OSPF as either type 1 (E1) routes or type 2 (E2) routes, with type 2 being the default. A type 1 route has a metric that is the sum of the internal OSPF cost and the external redistributed cost. A type 2 route has a metric equal only to the redistributed cost, as shown in Figure 14-2. If routes are redistributed into OSPF as type 2 then every router in the OSPF domain will see the same cost to reach the external networks. If routes are redistributed into OSPF as type 1, then the cost to reach the external networks could vary from router to router.

Figure 14-2Figure 14-2 OSPF Routes Are Redistributed as Either Type 1 or Type 2 Routes

Modify the configuration on Router B so that the EIGRP routes are redistributed as type 1 routes.

Router B
router ospf 1
 redistribute eigrp 1 metric 66 metric-type 1

Verification

Verify that the EIGRP routes have been redistributed into OSPF as type 1 routes with a metric of 66.

rtrB#show ip ospf database external
    OSPF Router with ID (2.2.2.2) (Process ID 1)
        Type-5 AS External Link States
 LS age: 149
 Options: (No TOS-capability, DC)
 LS Type: AS External Link
 Link State ID: 5.0.0.0 (External Network Number )
 Advertising Router: 2.2.2.2
 LS Seq Number: 80000008
 Checksum: 0xA638
 Length: 36
 Network Mask: /8
    Metric Type: 1 (Comparable directly to link state metric)
    TOS: 0
    Metric: 66
    Forward Address: 0.0.0.0
    External Route Tag: 0
 LS age: 158
 Options: (No TOS-capability, DC)
 LS Type: AS External Link
 Link State ID: 145.5.0.0 (External Network Number )
 Advertising Router: 2.2.2.2
 LS Seq Number: 80000008
 Checksum: 0x4706
 Length: 36
 Network Mask: /16
    Metric Type: 1 (Comparable directly to link state metric)
    TOS: 0
    Metric: 66
    Forward Address: 0.0.0.0
    External Route Tag: 0
 LS age: 168
 Options: (No TOS-capability, DC)
 LS Type: AS External Link
 Link State ID: 205.5.5.0 (External Network Number )
 Advertising Router: 2.2.2.2
 LS Seq Number: 80000008
 Checksum: 0x10B
 Length: 36
 Network Mask: /24
    Metric Type: 1 (Comparable directly to link state metric)
    TOS: 0
    Metric: 66
    Forward Address: 0.0.0.0
    External Route Tag: 0

Verify that the cost of these routes as seen by Router A is the sum of the redistributed metric and the OSPF cost to reach Router B.

rtrA#show ip route
Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGP
    D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
    N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
    E1 - OSPF external type 1, E2 - OSPF external type 2, E - EGP
    i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, ia - IS-IS inter area
    * - candidate default, U - per-user static route, o - ODR
    P - periodic downloaded static route
Gateway of last resort is not set
   1.0.0.0/32 is subnetted, 1 subnets
C    1.1.1.1 is directly connected, Loopback0
O E1 205.5.5.0/24 [110/1628] via 10.1.1.2, 00:05:36, Serial0/1
O E1 5.0.0.0/8 [110/1628] via 10.1.1.2, 00:05:36, Serial0/1
O E1 145.5.0.0/16 [110/1628] via 10.1.1.2, 00:05:36, Serial0/1
   10.0.0.0/30 is subnetted, 1 subnets
C    10.1.1.0 is directly connected, Serial0/1
4. Configuration Example 4: Redistributing Subnet Routes into OSPF as Type 1 Routes Using a Specific Metric | Next Section Previous Section