[nanog] Cisco GLBP/HSRP question -- Has it ever been dis

Tue Aug 6 12:59:13 UTC 2019

On Mon, Aug 5, 2019 at 11:38 AM Nicolas Chabbey <nchabbey at n3network.ch> wrote:
>
> Are there any good reasons of using proprietary FHRPs like HSRP and GLBP
> over VRRP ?

HSRP has an potential advantage over VRRP in that HSRP speakers keep
track of groups (virtual gateway clusters) in which they do not
participate.

The distinction could matter in a configuration where the routers all
participate in dynamic routing and might be generating ICMP redirects
to steer host traffic toward routers in different groups.

A VRRP router will redirect the client traffic toward the physical
interface of a (failure-prone) physical router (the redirect matches
the sending router's routing table).

An HSRP router recognizes that the preferred next-hop is participating
in an HSRP group, so it redirects the client traffic toward the VIP
associated with that group, rather than the physical router's
interface.

Since these redirects result in something akin to a static route in
the host device, it's safer to have that route pointing at a virtual
gateway than a physical interface.

You could easily convince me that any access LAN including multiple
routers participating in different FHRP groups is due for a redesign,
so this distinction might be moot. But I think it's a neat subtlety.

/chris