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4-12 CHAPTER 4: NETWORK CONFIGURATION TASKS
down. If a LEC cannot bind to the backup LES, it is necessary to check if
the LEC can connect to the LES and the LES can in turn, connect back to
the LEC. Correct E-IISP planning for route failover/redundancy is required
for LANE redundancy to work.
How Does The Primary LES Regain Control of the ELAN?
The primary LES will not automatically start serving the ELAN when it
becomes active again, if the backup LES is activated. Since doing so will
result in both LESs being active at the same time and also may possible
cause a VLAN split.
The LECS continues to serve/return the backup LES address (even when
the primary LES is active again) until the LECS is manually reset to start
serving the primary LES address for ELAN configuration requests.
Restoring LANE Clients To Use The Primary LES
Restoring the LANE clients to use the primary LES may be done in one of
the following ways:
1 Automatic recovery to the to primary LES when the backup LES fails
2 Manually returning the Clients (LECs) back to the primary LES.
Automatic Recovery to the Primary LES when the Backup LES Fails
The primary LES and its backup LES can be configured in the LECS
database to back each other up. Under such configuration, the network
will automatically revert to the primary LES when the backup LES fails.
For example, if LES A is the primary LES and LES B is its backup, the LECS
database will contain an additional entry after the first entry with LES B as
the primary LES and LES A as its backup.
Using this setup, when the primary LES fails, the LECs connect to the
backup LES and remain there even though the primary LES becomes
active again. When the backup LES fails, the LECs connect back to the
primary LES.
When the switch is becomes operative, if a new LEC wants to join the
LES, it joins the primary LES of the ELAN that is currently being served by
the backup LES. This would result in a split ELAN. This condition must be
carefully monitored and fixed manually by first fixing the LECS database
Redundancy Assistant) and then resetting the new LECs.