[c-nsp] OSPF Dampening

[Rodney Dunn]

Oh I'm going to be saying this a lot. :)


Look at EEM and write yourself a TCL policy that would monitor for
flap rate of an OSPF message in the syslog and block that
peer. 

ie: put an acl on the interface that blocks ospf packets coming
in from it.

Then start a script that pings the neighbor at a rate/time that you
feel determines the neighbor is back stable and then have the script
remove the ACL and let the neighbor come back up.

And you can have the EEM policy email you all along the way telling
you what it's doing. :)


Rodney


On Fri, Sep 29, 2006 at 09:02:15AM -0500, Jeremiah Millay wrote:
> In BGP there is a mechanism to dampen routes from a peer that is 
> flapping. Does anything similar to this exist for OSPF on a Cisco router?
> The closest thing I can find is this (IP Event Dampening):
> 
> http://www.cisco.com/en/US/products/sw/iosswrel/ps1839/products_feature_guide09186a0080110bc8.html
> 
> ...but it won't work for my setup because my interfaces don't flap, only 
> the OSPF adjacency is flapping.
> 
> Here is a crude diagram of my setup:
> 
> (a)------(b)
>  \          /
>   \        /
>     (c)
> 
> -Router A's primary path to router C is through B. This connection is 
> through a point-to-point wireless connection fed to the routers via ethernet
> - When the conenction from router A to B goes down, the link from A to C 
> is to become active.
> 
> I'm having problems with the radios failing between router A and B. 
> Because the ethernet link never goes down and it still receives hellos 
> sporadically the link from A to C never becomes active. On router A I 
> get log output similar to the following (and it repeats over and over):
> 
> *Sep 28 17:05:55: %OSPF-5-ADJCHG: Process 1, Nbr X.X.X.X on 
> FastEthernet0/0 from LOADING to FULL, Loading Done
> *Sep 28 17:06:56: %OSPF-5-ADJCHG: Process 1, Nbr X.X.X.X on 
> FastEthernet0/0 from FULL to DOWN, Neighbor Down: Dead timer expired
> *Sep 28 17:07:24: %OSPF-5-ADJCHG: Process 1, Nbr X.X.X.X on 
> FastEthernet0/0 from LOADING to FULL, Loading Done
> *Sep 28 17:09:03: %OSPF-5-ADJCHG: Process 1, Nbr X.X.X.X on 
> FastEthernet0/0 from FULL to DOWN, Neighbor Down: Dead timer expired
> *Sep 28 17:09:20: %OSPF-5-ADJCHG: Process 1, Nbr X.X.X.X on 
> FastEthernet0/0 from LOADING to FULL, Loading Done
> *Sep 28 17:10:44: %OSPF-5-ADJCHG: Process 1, Nbr X.X.X.X on 
> FastEthernet0/0 from FULL to DOWN, Neighbor Down: Dead timer expired
> 
> I would like to be able to dampen the routes from a neighbor when the 
> interface itself does not flap but the adjacency flaps. Is there any way 
> to do this or am I outta luck?
> Thanks in advance,
> Jeremiah
> 
> 
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