This topic is to discuss the following lesson:
You never really want to set backoff to anything but 90 90. So much so that Cisco chanaged the default timers in 15T to 90 90 because of customer demands. OER can take a long term to converge and when you start looking at things to cut down, the backoff timer is the easiest prey to be target for a change to the running config to optimize convergence to INPOLICY.
I have a question, how are backoff and holddown timers related?
I mean if holddown is set to 90 sec, but backoff is bigger, 300 sec, there will be a time after 90 sec that holddown is saying dont use the current route because its out of policy however as backoff time dont reach to 300 sec so router doesnt figure out yet an alternative path.
Maybe its first te holddown timer and then starts backoff timer and when it finish the router change path, so the timers are added.
Note that the holddown timer is a MINIMUM. This means that if it is set to 90, then for 90 seconds, the new exit MUST be used BEFORE any new alternative exit can be selected. If the 90 seconds are up, and there is not yet any new available exit, the current exit will still be used. It does not go out of policy. In other words, for 90 seconds, the exit is locked in and cannot be changed. After the 90 seconds, it can possibly, but not necessarily, be changed.
Alternatively, the backoff timer is the amount of time a router will wait after a route is out of policy, before attempting to find another exit path.
I hope this has been helpful!