Extreme Networks ExtremeWare XOS 11.3, Руководство пользователя

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Extreme Standby Router Protocol
ExtremeWare XOS 11.3 Concepts Guide
464
If a switch in slave mode loses its connection with the master, a new election (using the same
precedence order indicated
on page 462 or using a configured precedence order described in “ESRP
Election Algorithms” on page 465 ) occurs. The new election typically takes place in three times the
defined timer cycle (8 seconds by default).
Before the switch transitions to the master state, it enters a temporary pre-master state. While in the pre-
master state, the switch sends ESRP PDUs until the pre-master state timeout expires. Depending upon
the election algorithm, the switch may then enter the master or slave state. Traffic is unaffected by the
pre-master state because the master continues to operate normally. The pre-master state avoids the
possibility of having simultaneous masters.
You can configure the pre-master state timeout using the following command:
configure esrp <esrpDomain> timer premaster <seconds>
CAUTION
Configure the pre-master state timeout only with guidance from Extreme Networks personnel. Misconfiguration can
severely degrade the performance of ESRP and your switch.
ESRP Failover Time
ESRP Failover time is largely determined by the following factors:
●
ESRP hello timer setting.
●
ESRP neighbor timer setting.
●
The routing protocol being used for interrouter connectivity if Layer 3 redundancy is used; OSPF
failover time is faster than RIP failover time.
The failover time associated with the ESRP protocol depends on the timer setting and the nature of the
failure. The default hello timer setting is 2 seconds; the range is 2 to 1024 seconds. The default neighbor
timer setting is 8 seconds; the range is 3*hello to 1024 seconds. The failover time depends on the type of
event that caused ESRP to failover. In most cases, a non-hardware failover is less than 1 second, and a
hardware failover is 8 seconds.
If routing is configured, the failover of the particular routing protocol (such as RIP V1, RIP V2, or OSPF)
is added to the failover time associated with ESRP.
If you use OSPF, make your OSPF configuration passive. A passive configuration acts as a stub area and
helps increase the time it takes for recalculating the network. A passive configuration also maintains a
stable OSPF core.
For more information about the ESRP timers and configuring the ESRP timers, see the ExtremeWare XOS
Command Reference Guide .
ESRP Election Algorithms
You configure the switch to use one of 16 different election algorithms to select the ESRP master. ESRP
uses the default election policy for extended mode. If you have an ESRP domain operating in standard
mode, the domain ignores the sticky and weight algorithms.