By now, you probably understand why having a virtual router on a LAN is a great idea.
You also know why it’s a very good thing that the active router can change dynamically,
giving us much needed redundancy on our inside network. But what about the links to the
upstream network or the Internet connection off of those HSRP-enabled routers? And how
will the inside hosts know if an outside interface goes down or if they are sending packets
to an active router that can’t route to a remote network? Key questions and HSRP do provide
a solution for them called interface tracking.