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Cisco Frame Relay Configurations

Chapter Description

Jonathan Chin dicussess basic Frame Relay operations on Cisco routers in a router-based Frame Relay network. He also explains how to configure a basic frame relay network involving Cisco equipment and how to perform basic monitoring and troubleshooting using relevant Cisco IOS show and debug commands.

Local Significance Approach to DLCI Assignment

Earlier chapters discussed the concept of DLCI local significance. In the context of local significance on a Frame Relay network, the end devices at two different ends of a connection can use a different DLCI to refer to that same connection. This section discusses setting up a Frame Relay DLCI addressing scheme using the local significance approach to DLCI assignment. Later in the section, an alternate addressing scheme using the global significance approach is examined. Global significance of DLCI is part of the LMI enhancements to Frame Relay.

Figure 4-6 shows a hub-and-spoke Frame Relay network with five nodes using a DLCI scheme that conforms to the concept of local significance.

The configuration files of the Frame Relay switch for the network depicted in Figure 4-6 with the local significance addressing approach are shown in Example 4-28.

Figure 6Figure 4-6 Local Significance Addressing

Example 4-28 Configuration Files for Frame Relay Switch Using Local Significance Addressing

SW#show running-config
<output omitted>
hostname SW
!
no ip routing
!
frame-relay switching
!
interface Serial1/0
! Connection to Router Spoke A
 no ip address
 encapsulation frame-relay
 clockrate 64000
 frame-relay intf-type dce
 frame-relay route 201 interface Serial4/3 102
!
interface Serial1/1
! Connection to Router Spoke B
 no ip address
 encapsulation frame-relay 
 clockrate 64000
 frame-relay intf-type dce
 frame-relay route 301 interface Serial4/3 103
!
interface Serial1/7
! Connection to Router Spoke D
 no ip address
 encapsulation frame-relay
 clockrate 64000
 frame-relay intf-type dce
 frame-relay route 501 interface Serial4/3 105
!
interface Serial4/1
! Connection to Router Spoke C
 no ip address
 encapsulation frame-relay
 clockrate 64000
 frame-relay intf-type dce
 frame-relay route 401 interface Serial4/3 104
!     
interface Serial4/3
! Connection to the Hub Router
 no ip address
 encapsulation frame-relay
 clockrate 64000
 frame-relay intf-type dce
 frame-relay route 102 interface Serial1/0 201
 frame-relay route 103 interface Serial1/1 301
 frame-relay route 104 interface Serial4/1 401
 frame-relay route 105 interface Serial1/7 501

SW#show frame-relay route
Input Intf   Input Dlci   Output Intf   Output Dlci  Status
Serial1/0    201       Serial4/3    102      active
Serial1/1    301       Serial4/3    103      active
Serial1/7    501       Serial4/3    105      active
Serial4/1    401       Serial4/3    104      active
Serial4/3    102       Serial1/0    201      active
Serial4/3    103       Serial1/1    301      active
Serial4/3    104       Serial4/1    401      active
Serial4/3    105       Serial1/7    501      active
SW#

On a Frame Relay network using the global addressing approach, a unique DLCI address is assigned to each Frame Relay DTE device, including routers. The global addressing scheme allows Frame Relay devices to be uniquely identified by their assigned DLCIs. However, similar to the constraints of IP addressing, an assigned DLCI value cannot be reused in any other parts of the same Frame Relay network. In addition to this constraint, the number of Frame Relay devices that can be supported by global addressing is limited. Because global addressing requires the DLCI values to be unique, the maximum number of Frame Relay devices allowed is 992 (1024 possible DLCI values – 32 reserved DLCI addresses). Figure 4-7 presents an example of a Frame Relay network utilizing the global addressing scheme.

Figure 7Figure 4-7 Global Significance Addressing

The configuration files of the Frame Relay switch for the network depicted in Figure 4-7 with the global significance addressing approach are shown in Example 4-29.

Example 4-29 Configuration Files for Frame Relay Switch Using Global Significance Addressing

SW#show running-config
<output omitted>
hostname SW
!
no ip routing
!
frame-relay switching
!
interface Serial1/0
 ! Connection to Router Spoke A
 no ip address
 encapsulation frame-relay
 clockrate 64000
 frame-relay intf-type dce
 frame-relay route 101 interface Serial4/3 201
!
interface Serial1/1
 ! Connection to Router Spoke B
 no ip address
 encapsulation frame-relay
 clockrate 64000
 frame-relay intf-type dce
 frame-relay route 101 interface Serial4/3 301
!
interface Serial1/7
 ! Connection to Router Spoke D
 no ip address
 encapsulation frame-relay
 clockrate 64000
 frame-relay intf-type dce
 frame-relay route 101 interface Serial4/3 501
!
interface Serial4/1
 ! Connection to Router Spoke C
 no ip address
 encapsulation frame-relay
 clockrate 64000
 frame-relay intf-type dce
 frame-relay route 101 interface Serial4/3 401
!     
interface Serial4/3
 ! Connection to the Hub Router
 no ip address
 encapsulation frame-relay
 clockrate 64000
 frame-relay intf-type dce
 frame-relay route 201 interface Serial1/0 101
 frame-relay route 301 interface Serial1/1 101
 frame-relay route 401 interface Serial4/1 101
 frame-relay route 501 interface Serial1/7 101
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