
Configuring Dial Services
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Link backup is a multiple-circuit backup, which means that the entire interface is
backed up. To back up all PVCs for a frame relay interface, you configure frame
relay across the backup circuit.
Figure 1-8
shows an example of link backup.
Figure 1-8. Link Backup for a Frame Relay Network
In Figure 1-8, if the frame relay link fails at router R1, the router activates a
backup connection through the ISDN network, then back through the frame relay
network to the destination. The backup connection to the frame relay network uses
a different network interface and PVCs than the primary connection. After the
primary line recovers and the frame relay switch responds to router R1’s DLCMI
status requests, router R1 terminates the backup connection.
Note:
A primary circuit cannot use link and circuit backup simultaneously.
Frame relay
network
ISDN
network
Frame relay
interface
BRI
PRI
Central site router (R2)
Failure point
Group mode PVCs
Primary PVCs
Backup PVCs
DS0026A
Remote site router (R1)
Key
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