Chapter 19. First-Hop Redundancy
First-hop redundancy is the ability for one or more devices to share the same IP address in order to provide multidevice resiliency in default gateway scenarios (though they can be nondefault gateways, too). Usually, this involves one device owning the IP address while other devices stand by, ready to assume control of the address should the owner fail. This is not always the case, however, as we’ll see.
Cisco’s proprietary Hot Standby Router Protocol (HSRP) is probably what most Cisco shops are using to accomplish this, but outside of the Cisco world the Virtual Router Redundancy Protocol (VRRP) is the standard. This is likely due to the fact that it is an open source protocol and therefore supported by multiple vendors. Arista’s Extensible Operating System (EOS) supports VRRP, but also introduces an interesting new feature called Virtual Address Resolution Protocol (VARP). In this chapter, we take a look at both VRRP and VARP, including configuration examples and reasons why you might choose one solution over the other.
If all you’ve ever used is Cisco’s HSRP, don’t worry, because VRRP is pretty much the same thing. In fact, it’s so similar that Cisco complained vigorously when the RFC for VRRP was announced. VRRP is defined in RFCs 2338, 3768, and 5798, whereas Cisco’s HSRP is defined in RFC 2281. The RFC for HSRP states the following:
2 Conditions of Use US Patent number 5,473,599 , assigned to Cisco Systems, Inc. may be applicable ...