Frame Relay Switching

Frame Relay Switching

When setting up a Frame Relay DCE device, we need to follow the following steps. 1. Enable Frame Relay Switching 2. Change The interface type 3. Glue the DLCIs together

Enable Frame Relay Switching

The command is ultra simple, but without it the device will try to decapsulate the frames and look up the Layer 3 information. This is not needed on a Frame Relay Switch.
FRS(config)# frame-relay switching

Change the interface type

Interfaces connected to DTE routers must be set to DCE to enable LMI
FRS(config-if)# frame-relay intf-type dce
On interfaces connecting to other Frame Relay switches, the type must be set to nni – Network-to-Network Interface
FRS(config-if)# frame-relay intf-type nni

Glue the DLCIs together

There are 2 methods for connecting a DLCI on an interface to a DLCI on another interface. The old method needed two commands, one for each interface, like this:
FRS(config)# interface INTERFACE-1
FRS(config-if)# frame-relay route DLCI-1 interface INTERFACE-2 DLCI-2
FRS(config-if)# exit
FRS(config)# interface INTERFACE-2
FRS(config-if)# frame-relay route DLCI-2 interface INTERFACE-1 DLCI-1
To verify, use:
FRS#sh frame-relay route
Input Intf Input Dlci Output Intf Output Dlci Status
Serial1/1 102 Serial1/2 201 inactive
Serial1/2 201 Serial1/1 102 inactive
The newer method needs just one command in the global config:
FRS(config)# connect CONN-NAME INTERFACE-1 DLCI-1 INTERFACE-2 DLCI-2
and to verify, use:
FRS1#sh connection all
ID Name Segment 1 Segment 2 State
========================================================================
1 R1R2 Se1/1 102 Se1/2 201 UP

Switching over a Tunnel interface

There are situations where you have Frame Relay routers as Provider edge, but use another technology as the Provider Core. You can still perform Frame Relay Switching by tunneling the Frames from one PE router to another
You must configure the frame relay interfaces similarly on the two Frame Relay switches and then configure the Tunnel interface on each router:
FRS(config)# interface TUNNEL0
FRS(config-if)# tunnel source {INTERFACE|SRC-IP-ADDR}
FRS(config-if)# tunnel destination {INTERFACE|SRC-IP-ADDR}
FRS(config-if)# ip {unnumbered INTERFACE| address TUN-IP-ADDR}
Then create the frame-relay routes, making sure you use the same DLCI on the Tunnel interface on both routers:
!On FRS1
FRS1(config)# interface INTERFACE-1
FRS1(config-if)# frame-relay route DLCI-1 interface TUNNEL0 DLCI-TUN
!On FRS2
FRS2(config)# interface INTERFACE-2
FRS2(config-if)# frame-relay route DLCI-2 interface TUNNEL0 DLCI-TUN
You cannot use the connect command to create the routes.
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Frame Relay Switching
Enable Frame Relay Switching
Change the interface type
Glue the DLCIs together
Switching over a Tunnel interface