OSPF and Interface Reliability Problems !!!

[g.oridota]

I need help please with a current issue where OSPF continues to pass traffic via a Radio link whose reliability has dropped considerably ( 190/ 255 ) . Is there any mechanism on the Router that can be tweeked such that once the reliability drops , OSPF can see that as an interface down and hence re-route traffic ?

[dknov]

Hi,

Unfortunately no :( Interface reliability is not one of the parameters considered by OSPF for cost calculation, only interface configured (or default)bandwidth is.

The only thing I can think of is use static routes with tracking option for SAA (former RTR) probe. Your IOS needs to support it and also it's moving to static which might not be feasible in every situation.

1. Create SAA probe (RTR instance) and set it's type accordingly. Now the idea is to assume that once interface reliability drops, you will start loose some data and that's when you hope this SAA probe will reach it's maximum configured limit of reties.

2. Create static route and in the end of the "ip route" command specify the tracking object (equal to RTR instance ID). You can optionally redistribute this static into OSPF

3. Once SAA probe "goes to down", it will make the static route disappear from routing table and router will stop forwarding traffic through the link. Additionally if you had configured to redistribute it into OSPF, once it disappears from routing table, OSPF will not redistribute it anymore and you will get the same result.

Hope that gave you some ideas.

David