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We are wanting to add a second PE router for an MPLS customer via HSRP. Unfortunately the CE router's connection to the PE router was configured as a /30. There are no IP addresses on the subnet to use as the physical IP addresses of the HSRP routers and re-IP'ing the customer's network is not an option.

HSRP will not run without a physical, in addition to virtual, IP address on the interface. If I place the physical address on a different subnet, I get similar behavorior to what is described in the Packet Life link below.

"show standby" lists the state as "Init (virtual IP in wrong subnet)".

http://packetlife.net/blog/2008/may/24/dont-cheat-on-hsrp-addressing/

Is there a way to use HSRP on an interface that has a /30 subnet?

  • I can think of an unnatural hack without resorting to Jeremy's method to make /30 + HSRP work, but it will be a while (several days) before I can post it all... can you wait? – Mike Pennington Apr 16 '14 at 9:33
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No way to do HSRP. I can think of one way to do it though. (never seen in production, just for the sake of answering your question) Solution: Use private subnet(at least /29) on the PE and CE interfaces, use your /30 on an GRE tunnel interfaces. GRE between PE interface IP and CE HSRP IP.

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