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Chapter 13: AI2524 Frame Relay Configuration Steps
August 1997 Page 13-27
2524UM
Example: Transparent Bridging Using Subinterfaces
In this example, Frame Relay DLCIs 42, 64, and 73 are to be used as
separate point-to-point links with transparent bridging running over
them. The bridging spanning tree algorithm views each PVC as a sep-
arate bridge port, and a frame arriving on the PVC can be relayed back
out a separate PVC. Be sure that routing is not enabled when config-
uring transparent bridging using subinterfaces.
interface serial 0
encapsulation frame-relay
interface serial 0.1 point-to-point
bridge-group 1
frame-relay interface-dlci 42
interface serial 0.2 point-to-point
bridge-group 1
frame-relay interface-dlci 64
interface serial 0.3 point-to-point
bridge-group 1
frame-relay interface-dlci 73
Configure a Backup Interface for a Subinterface
Both point-to-point and multipoint Frame Relay subinterfaces can be
configured with a backup interface. This approach allows individual
PVCs to be backed up in case of failure rather than depending on th
entire Frame Relay connection to fail before the backup takes over.
You can configure a subinterface for backup on failure only, not for
backup based on loading of the line.
If the serial interface has a backup interface, it will have precedenc
over the subinterface's backup interface in the case of complete loss o
connectivity with the Frame Relay network. As a result, a subinterface
backup is activated only if the serial interface is up, or if the serial in-
terface is down and does not have a backup interface defined. If a sub-
interface has failed while its backup is in use, and then the serial
interface goes down, the subinterface backup stays connected.
Beginning in global configuration mode, configure a backup interface
for a Frame Relay subinterface:
1. Specify the interface.
interface serial
number
2. Configure Frame Relay encapsulation.
encapsulation frame-relay