Help with HSRP

Unanswered Question
Jul 22nd, 2008

I'm trying to implement HSRP for redundancy between two Gateway Routers. The problem is currently there is no dynamic routing setup for testing purposes. So there are only static routes in the gateway. That causes a problem for me if I give a new virtual ip to the main Gateway since all my traffic is forwarded to the current ip address. My question is can I use the same ip address that is currently used for my primary gateway as my virtual ip?

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izackvail Tue, 07/22/2008 - 09:25

You can make your current gateway IP the virtual IP as long as you change the interface IP for that gateway to something else. The standby IP and interface IP cannot be the same.

uzmausmani Tue, 07/22/2008 - 09:32

But the virtual IP wont be triggered until the current gateway goes down.. so how will the traffic flow normally since the traffic is currently pointing to the current IP configured on the interface. If I change the interface IP the traffic would only be flowing to the virtual IP which doesnt come into place until the Router goes down or does it?

Edison Ortiz Tue, 07/22/2008 - 10:30

If you remove the IP address from the physical interface and assign this IP address to the HSRP Virtual IP, traffic towards the 'gateway' will be momentarily disrupted while you making the changes. Therefore, I suggest making these changes during a maintenance window.

I'm not sure what you mean by this statement

"virtual IP wont be triggered until the current gateway goes down."

The Virtual IP will be active as soon as you remove the IP from the physical interface, assign a new IP on this physical interface, then relocate the IP from the physical interface to the HSRP Virtual IP.




uzmausmani Tue, 07/22/2008 - 10:44

oh so you're saying I should simply set the current gateway IP as the virtual IP and give a different IP to the physical interface (currently the default gateway address) and still the traffic would be routed to the virtual IP and not the IP of the physical interface? If this works then thats great. Please confirm that I understand correctly. and thanks a billion!!

Edison Ortiz Tue, 07/22/2008 - 11:00

Yes, that's the message we are trying to convey.




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lgijssel Tue, 07/22/2008 - 11:19

Your problem will be with the arp tables. The hsrp-adress will be reachable via a virtual mac adress. This will be a different mac-adress as the one you currently use.

The disruption is caused while the PC's have to learn the new mac adress.



uzmausmani Tue, 07/22/2008 - 11:42

But that should only take a while until they learn the new mac address via arp...right?

ecarabias Wed, 08/06/2008 - 04:24


The command "h323-gateway voip bind srcaddr" only accepts the physical IP address, no the standby IP address.


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