Product guide

Router Redundancy Using XRRP
Overview of XRRP Operation
Fail-Over Operation with Infinite Fail-Back Enabled
XRRP
Protection
Domain
Server
Layer 2
Switch
Router “B”
Router “A”
Layer 2
Switch
Server
Server
Figure 12-6. Example of XRRP Routers in a Protection Domain
When XRRP is enabled on router “A” with infinite fail-back already enabled
in the configuration, the router immediately waits for a period equal to three
times the XRRP advertisement interval to determine the current fail-back
mode of its XRRP peer router “B”. Depending on the result of the waiting
period, router “A” assumes one of the following modes:
■ primary control only: occurs if router “B” is doing one of the following:
• running with only primary control mode.
• running with primary and secondary control mode, but has not
detected a prior fail-over on router “A”. (This can occur if a failed
router is replaced with another XRRP router.)
■ primary and secondary control: occurs if router “B” is in a fail-over
mode.
■ fail-over: occurs if router “B” has detected a prior fail-over on router “A”
and is in the primary and secondary control mode as a result.
Router Operation in the Fail-Over Mode
An XRRP router that has failed-over to a peer (fail-back router) in a protection
domain (where both routers are configured with infinite fail-back), and then
recovers, remains in the fail-over mode unless the status of the fail-back router
changes as described under <zBlue>“Router Operation in the Infinite Fail-
Back Mode”, below. This means that changes solely in the status of the failed-
over router, such as recovery of all its XRRP VLANs, cannot initiate a fail-back
from the peer router.
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