Steven Bellovin wrote:
VRRP? The Router Discovery Protocol (RFC 1256). But given how much more reliable routers are today than in 1984, I'm not convinced it's that necessary these days.
VRRP is an absolutely essential protocol in today's Internet. We use it on every non-bgp customer port. Routers still have routing and performance issues, hardware failures and routine software upgrades. The layer2 infrastructure between the routers and the customer is also susceptible to various hardware/software/maintenance problems and fiber cuts and VRRP can help work around some of those. A nice side benefit is the virtual mac addresses that allow for migration to new routers without the mac address of the default gateway changing. One key advantage of VRRP over RA's is that you can have multiple instances on the same layer2 network (vlan) with different functions. It is very common to have different "routers" (routers, firewalls or load balancers) on the same vlan with different functions in hosting environments. It is also sometimes necessary to have multiple default gateways on the same vlan for load balancing or traffic engineering. RA/auto configuration is incompatible with all but the most trivial configurations. - Kevin