Brocade Communications Systems ServerIron ADX 12.4.00 Service Manual download pdf (Page 188)

ServerIron ADX Firewall Load Balancing Guide 177

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Configuring failover tolerance in IronClad configurations

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Configuring failover tolerance in IronClad configurations

By default, failover from the active ServerIron ADX to the standby ServerIron ADX in an IronClad

configuration occurs if a path link on the active ServerIron ADX becomes unavailable. If all the path

links are stable, failover is an uncommon event. However, an unreliable link can cause frequent

failover. For example, if a link on a firewall flaps (goes up and down) frequently, the flapping can

cause frequent, unnecessary failovers.

You can reduce the frequency of such failovers by specifying a path link tolerance for firewall paths

and for router paths. The tolerance specifies the minimum number of such paths that must be

good in order for the active ServerIron ADX to remain active. Only if the number of paths is less than

the configured minimum and less than the number of available paths on the other ServerIron ADX

does failover occur. If the number of paths remains equal on each ServerIron ADX, even if some

paths are unavailable on each ServerIron ADX, failover does not occur.

The default failover tolerance for firewall paths is one half the configured firewall paths. The default

tolerance for router ports is one half the configured router ports.

To change the minimum number of paths required on a ServerIron ADX, use the following method.

NOTE

The minimum number of required paths must match on each ServerIron ADX in an active-standby

pair. For example, if you specify one router path and three firewall paths as the minimum on the

active ServerIron ADX, you must configure the same minimums on the standby ServerIron ADX.

To specify the minimum number of paths required on a ServerIron ADX, enter the following

commands.

ServerIronADX(config)# server fw-group 2

ServerIronADX(config-fw-2)# prefer-router-cnt 1

ServerIronADX(config-fw-2)# prefer-cnt 3

This example specifies that a minimum of one router path and three firewall paths must be

available for the ServerIron ADX to remain active. Thus, if the ServerIron ADX has four firewall

paths, one path can be unavailable and the ServerIron ADX will remain the active ServerIron ADX.

Syntax: [no] prefer-router-cnt <num>

Syntax: [no] prefer-cnt <num>

For each command, the <num> parameter specifies the minimum number of paths required.

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Brocade Communications Systems ServerIron ADX 12.4.00 Service Manual Page 188