hsrp - setting up dedicated back to back interface

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May 29th, 2008
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Hi all, If I have 2 routers, with 2 interfaces, and I want hsrp between the 2 routers, the main lan is plugged into int fa0/1 and the back to back for hsrp is plugged into int fa 0/0, how would I configure this?

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Kevin Dorrell Thu, 05/29/2008 - 05:41
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I think you have a conceptual problem here. HSRP does not use a back-to-back connection.


Essentially, HSRP allows two routers to handle the routing from a LAN or VLAN. Both routers should be on "the main LAN", as you put it. The HSRP happens on this "main LAN". What it means is that the two routers share a single IP address: one in active, and one in standby. And it is that single address that the hosts use as a default gateway.


Have a serach on cisco.com ... there are loads of documents that tell you how to do this. Much better that, than have someone type it all out here.


Kevin Dorrell

Luxembourg


carl_townshend Fri, 05/30/2008 - 01:34
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Is there any reason why my isp would use a back to back connection on the router then ? I thought it was for hsrp ?

Kevin Dorrell Fri, 05/30/2008 - 02:45
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The HSRP is always in a LAN that servers hosts,not in a back-to-back situation.


It could be that they use the back-to-back as a routed connection so that if one of the uplinks goes down, both routers can still see the ISP.


If the routers are running HSRP on the LAN side, normally you would handle this by getting the HSRP to track the state of the uplink, and/or the state of the default route. Maybe they chose to do it a different way. You will have to ask them.


Kevin Dorrell

Luxembourg


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