Cisco PIX 500 Series Configuration Manual page 246

Configuring Failover
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Configuring Interface Health Monitoring
The security appliance sends hello packets out of each data interface to monitor interface health. If the
security appliance does not receive a hello packet from the corresponding interface on the peer unit for
over half of the hold time, then the additional interface testing begins. If a hello packet or a successful
test result is not received within the specified hold time, the interface is marked as failed. Failover occurs
if the number of failed interfaces meets the failover criteria.
Decreasing the poll and hold times enables the security appliance to detect and respond to interface
failures more quickly, but may consume more system resources.
To change the interface poll time, enter the following command in global configuration mode:
hostname(config)# failover polltime interface [msec] time [holdtime time ]
Valid values for the poll time are from 1 to 15 seconds or, if the optional msec keyword is used, from
500 to 999 milliseconds. The hold time determines how long it takes from the time a hello packet is
missed to when the interface is marked as failed. Valid values for the hold time are from 5 to 75 seconds.
You cannot enter a hold time that is less than 5 times the poll time.
If the interface link is down, interface testing is not conducted and the standby unit could become active
Note
in just one interface polling period if the number of failed interface meets or exceeds the configured
failover criteria.
Configuring Failover Criteria
By default, a single interface failure causes failover. You can specify a specific number of interfaces or
a percentage of monitored interfaces that must fail before a failover occurs.
To change the default failover criteria, enter the following command in global configuration mode:
hostname(config)# failover interface-policy num [%]
When specifying a specific number of interfaces, the num argument can be from 1 to 250. When
specifying a percentage of interfaces, the num argument can be from 1 to 100.
Configuring Virtual MAC Addresses
In Active/Standby failover, the MAC addresses for the primary unit are always associated with the active
IP addresses. If the secondary unit boots first and becomes active, it uses the burned-in MAC address for
its interfaces. When the primary unit comes online, the secondary unit obtains the MAC addresses from
the primary unit. The change can disrupt network traffic.
You can configure virtual MAC addresses for each interface to ensure that the secondary unit uses the
correct MAC addresses when it is the active unit, even if it comes online before the primary unit. If you
do not specify virtual MAC addresses the failover pair uses the burned-in NIC addresses as the MAC
addresses.
You cannot configure a virtual MAC address for the failover or Stateful Failover links. The MAC and IP
Note
addresses for those links do not change during failover.
Cisco Security Appliance Command Line Configuration Guide
14-26
To enable health monitoring for an interface, enter the following command in global configuration
mode:
hostname(config)# monitor-interface if_name
Chapter 14 Configuring Failover
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