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Cisco announces new innovations in SD-WAN, ISRs, SD-WAN Services, and Catalyst 9000 Series switches


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Participant

HSRP with direct link failure

Hi all,

 

I have a scenario where I dont really know what to do with it.

 

I have two SP routers connecting to my LAN and providing us with two Internet connections.

Those two routers have HSRP configured on the LAN side and are connected to a switch to which also my FW is connected to.

Now the other day we had a link failure on the switch, basically isolating the HSRP "active" router. That created a situation where the "active" router stayed active as it wasnt able to talk to its peer anymore, but furthermore the "standby" also became active as it couldnt talk to the "active" anymore and assumed it to be dead.

 

Now I was thinking about how to prevent such a situation in the future and thought about IP SLA. With IP SLA I could e.g. track reachablility of our FW IP and if its lost, decrement the HSRP priority of the "active", making it go to "standby"!? But then what if its not the interface on the switch that the router is connected to, but the FW interface that is faulty? There would be a HSRP change for no reason. So tracking FW reachability does not really help here I guess? As the switch is a L3 switch, I could create a loopback interface on the switch and track that!? But what if the router interface on the switch fails, through IP SLA the HSRP prio on the "active" one would decrement, but as the peers cant speak with each other anymore would the "active" go into standby then? I dont think so...

 

I would appreciate any input on that matter! How did/ would you implement such a scenario?

 

BR

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VIP Advisor

Re: HSRP with direct link failure

Hello

If applicable you could physically attached the rtrs together and track their lan and wan interfaces for reachability or line state.

This way you wont incurr the issue with a faulty switch negating the hrsp hellos to between routers



kind regards
Paul

Please don't forget to rate any posts that have been helpful.
Participant

Re: HSRP with direct link failure

Hi Paul,

 

thanks for your reply.

 

Can you please elaborate on your thought. I dont really know what you mean.

Right now Iam able to ping the LAN IP of the peer router but thats pretty much the same as sending HSRP hello packets, no?

 

BR

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VIP Advisor

Re: HSRP with direct link failure

Hello

Can you physically connect a cable between your two hrsp rtrs instead of them both going via a switch for hrsp?



kind regards
Paul

Please don't forget to rate any posts that have been helpful.
Participant

Re: HSRP with direct link failure

Hi Paul,

 

thanks again for your reply.

 

Well, I need to connect them to a switch as they provide the default GW for my LAN, which in turn is connected to that switch.

Or do I have some error in reasoning?

If I would have two L3 switches I could connect an additional link between the two and put that connection in the same Vlan, creating a loop technically. But would that help?

 

BR

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