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Participant

OSPF conditional (not default route) routing

Hello,

 

I know that there're some possibilities with default route to be conditionally advertised using ospf and route maps.

 

But do it's possible to somehow tell OSPF: if some address is reachable via ping (using SLA for example) then advertise and receive all routes from particular neighbor. But if some IP is not reachable via PING then stop advertising and receiving everything via that neighbor.

 

Did my search, haven't see anything.

 

Thank you

 

 

 

6 REPLIES 6
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VIP Mentor

Re: OSPF conditional (not default route) routing

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Hall of Fame Master

Re: OSPF conditional (not default route) routing

Hello @from88 ,

as far as I know OSPF allows for conditional advertising only for the default route and not for more specific prefixes.

You can use BGP that supports conditional advertising to achieve the desired behaviour.

You can keep OSPF to advertise loopback addresses and then configure iBGP between loopbacks like you were a service provider.

 

OSPF being a link state  IGP protocol can only advertise or not advertise a prefix related to the status of a link.

 

Hope to help

Giuseppe

 

Highlighted
VIP Expert

Re: OSPF conditional (not default route) routing

Yes I believe it's possible if the device supports EEM.

If EEM detects lost response to an IP it deactivates the OPSF to the neighbor you want to "suppress". When it see the response again, it reactivates the OSPF to the neighbor.
Highlighted
Participant

Re: OSPF conditional (not default route) routing

thank you all. Sad, but old C2960X dont have even EEM. :)
Highlighted
VIP Expert

Re: OSPF conditional (not default route) routing

Ah, well that would spike that. I haven't looked myself, but no EEM with latest IOS and/or a non Lite/Base feature set?

 

PS:

Oh, another approach, if you cannot do EEM on the switch itself, would be to logically do the same thing, but physically from another scripting host.

Highlighted
Participant

Re: OSPF conditional (not default route) routing

Thanks, seems one of the newest IOS version has it:) https://www.cisco.com/c/en/us/td/docs/ios-xml/ios/eem/configuration/15-mt/eem-15-mt-book/eem-overview.html#GUID-A33C0359-B4BE-46FE-8992-0D468A246E4A

 

Actually this is one of the workarounds for problem mentioned here: https://community.cisco.com/t5/data-center-switches/failure-of-data-plane-traffic-has-anybody-experienced/td-p/4096167

 

We experienced this type of dataplane failure of the uplink switch, so i thought maybe i will use EEM to disable OSPF on condition: when C2960x uplink port to Athe time failed NEXUS is UP, but the ping to neighboring p2p address fails.