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Is it possible to associate IP SLA with BGP conditional advertisement

Is it possible to associate object tracking IP SLA with BGP conditional advertisement?

If I only use the BGP conditional advertisement then I will still need to wait for the route timeout but the user application can't wait that long so I am wondering if anyway to associate the object tracking with conditional advertisement.

Or if there is any work around to withdraw the BGP route when remote route not reachable immediately?

1 ACCEPTED SOLUTION

Accepted Solutions
Hall of Fame Super Bronze

Re: Is it possible to associate IP SLA with BGP conditional adve

The problem I've seen with MPLS and CSC is broken labels in the path.

The BGP session (PE<->PE) will remain up and the routes will be in the table but there is a blackhole. Nasty scenario.

What I've seen done to workaround this dilemma is to advertise loopbacks from the CE to the MPLS Backbone via BGP and create another BGP peer CE<->CE with those loopbacks. As soon as the loopbacks aren't reachable, the BGP session will go down.

HTH,

__

Edison.

11 REPLIES
Hall of Fame Super Silver

Re: Is it possible to associate IP SLA with BGP conditional adve

Hello Frank,

I'm afraid this is not possible however, using aggressive timers on the primary BGP session and neighbor ... fall-over should help to minimize the detection time.

By default in modern IOS images ebgp fast external fallover is enabled and as soon as the outgoing interface is detected down the session is torned down and this should trigger also BGP conditional advertisement

Hope to help

Giuseppe

New Member

Re: Is it possible to associate IP SLA with BGP conditional adve

Giuseppe,

Thanks for the reply.

We are facing some outage inside the MPLS cloud and is not local circuit outage and the customer want to fail to their backup circuit ASAP instead of waiting for BGP timeout... We have tuned the BGP advertisement interval but still not good enough for their apps.

So we are trying to use some tracking mechanism to re-route the traffic ASAP.

I am thinking to use conditional injection instead of advertisement and will test it in our lab...

New Member

Re: Is it possible to associate IP SLA with BGP conditional adve

Hi...

Have you looked into BGP BFD (Bi-directional Forwarding Detection) ?

Thanks...

Vyto

New Member

Re: Is it possible to associate IP SLA with BGP conditional adve

Yes, we think about that but the PE from carrier doesn't allow the BFD and it is not local outage but someing inside the cloud so we are looking for end-to-end tracking to influence the routing.

Hall of Fame Super Bronze

Re: Is it possible to associate IP SLA with BGP conditional adve

The problem I've seen with MPLS and CSC is broken labels in the path.

The BGP session (PE<->PE) will remain up and the routes will be in the table but there is a blackhole. Nasty scenario.

What I've seen done to workaround this dilemma is to advertise loopbacks from the CE to the MPLS Backbone via BGP and create another BGP peer CE<->CE with those loopbacks. As soon as the loopbacks aren't reachable, the BGP session will go down.

HTH,

__

Edison.

New Member

Re: Is it possible to associate IP SLA with BGP conditional adve

Edison,

Yeap, what a coincident that one of our guys talk about GRE end-to-end then we go further for EBGP multi-hops end-to-end and tune the timer very low...

I think it is a better way instead of doing tracking with conditional injection.

I will test that in our lab then propose to the client.

Thanks.

Hall of Fame Super Bronze

Re: Is it possible to associate IP SLA with BGP conditional adve

GRE is another approach but you will face the common issues associated with GRE, fragmentation and such.

Hall of Fame Super Silver

Re: Is it possible to associate IP SLA with BGP conditional adve

Hello Edison,

very good idea!

Best Regards

Giuseppe

Hall of Fame Super Bronze

Re: Is it possible to associate IP SLA with BGP conditional adve

Giuseppe,

grazie :)

Re: Is it possible to associate IP SLA with BGP conditional adve

Frank,

This has to do with Ebgp updates, Object tracking is not applicable here neither Fast external failover feature.

The Conditional Advertisment relies on the BGP routing table, therfore, relies on the ebgp routing update which is 30sec by default.

If you need to have rapid routing convergence, you could change the BGP Scanning time for that update although its not recommended as this could seriously impact your memory resources of the router.

HTH

Mohamed

Re: Is it possible to associate IP SLA with BGP conditional adve

Edison,

Good that you have observed that, At least the LSPs , CSC , and PE-PE.

looks like you have been tackling the passed CCIS service provider track....

Regards,

Mohamed

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