Static Route Adjustment Interval

richlarkins · ‎07-24-2009

I'm confused about static route adjustment interval.

I have two 6509's running HSRP. There are networks that are statically routed through the HSRP interface. Each 6509 has static weights assigned to each route for failover.

The question I have is: Does static route adjustment interval only work on a single IOS device to update the routing table, or would it have an impact on my fail-over, fail-back of the static routes over the HSRP interface?

Giuseppe Larosa · ‎07-24-2009

Hello Richard,

according to following document

http://www.cisco.com/en/US/docs/ios/12_0s/feature/guide/fs_sradj.html

describing the feature you can see this as the time it takes to remove a static route in the local node once the next-hop is unreachable.

>>

Time of delay, in seconds, for convergence time during which the background process that monitors next-hop reachability is performed. The delay in convergence occurs when the route that covers the next-hop is removed. The range is from 1 to 60. The default is 60.

By using an HSRP VIP as the IP next-hop of static routes this mechanism is not triggered because the VIP is emulated both at L3 and at L2 (unless using standby use-bia).

Unless the check frequency is less then HSRP convergence time the local node never realizes of an HSRP switchover.

With default values HSRP convergence happens in 10 seconds and the timer for static checks is 60 seconds.

I think it is better to have HSRP convergence time less then this check interval or the usage of HSRP is defeated.

if the node detects failure of current VIP it removes the route from routing table before HSRP switchover.

Hope to help

Giuseppe