When an ISA transitions from a standby to an active state, the timeout for the synchronized flows on the newly active ISA is set to a percentage of the flow timeout value that is configured in the NAT policy. Timeout of the flow refers to the clearing of its state in NAT after a period of traffic inactivity. Flow timeouts are configured in the NAT policy. This adjustment of the flow timeout on the newly active ISA is necessary because the standby ISA, although aware of the flows, is not aware of the flow forwarding status at the time of the switchover. In other words, the flow on the active node just before the switchover may have been inactive and close to the timer expiry. In this case, it may not be desirable to extend the life time of such a flow on the newly active ISA to its initially configured value.
This flow timeout after the switchover is set by the following command:
config>isa>nat-group>inter-chassis-redundancy>flow-timeout-on-switchover percent [1..50]
A value of 50 for the flow-timeout-on-switchover means that synchronized flows on the newly active ISA inherits half of the value set in the NAT policy.