Hot Standby Router Protocol (HSRP) Overview: You’ve Got A Friend

When you’re down and troubled and you need a helping hand
And nothing, whoa, nothing is going right
Close your eyes and think of me and soon I will be there
To brighten up even your darkest nights

You just call out my name, and you know wherever I am
I’ll come running, oh yeah baby, to see you again
Winter, spring, summer, or fall
All you got to do is call and I’ll be there, yeah, yeah, yeah
You’ve got a friend

Whenever I see Hot Standby Router Protocol (HSRP), it always reminds me of a song. As what James Taylor said, “You’ve Got a Friend.” If you already know what HSRP is, you might’ve as well other things that make you remember what it does.

If you’re kinda new and trying to understand what this is, this is a good start as I will not make this topic complicated. Although there are lots of things to tackle with HSRP, we will stick with the basics and some links are provided below to further discuss other HSRP topics.

HSRP is not a router and definitely not a routing protocol. When I first studied HSRP, the first thing that came up in my mind is that this is a routing protocol like EIGRP, BGP, OSPF, or RIP but it isn’t as it does not affect the routing table.

HSRP is a Cisco proprietary redundancy protocol. One device will act as active and the other is passive. Once the active device is down, the passive device will take over. The active device will be responsible for handling the traffic of the VIP (virtual IP). Since the VIP is shared between these two devices, when the active device fails, traffic will failover to the standby device. However, keep in mind that pre-emption is not enabled by default.


BGP Neighbor Adjacency States: From IDLE to ESTABLISHED

BGP requires manual configuration of neighbors. Once neighbors are manually configured, it goes through 6 states until it is fully established. Knowing these states would help us determine the stage our connection is currently in. It is also very important in troubleshooting as it helps us understand what went wrong during adjacency.

BGP Neighbor Adjacency States

BGP Neighbor Adjacency States:

1. IDLE – This is normally can be seen if BGP is down / administratively down or just waiting for the next attempt. At this stage, no BGP incoming sessions are permitted.

My BGP is established between Culloden and Stirling sites and Culloden and Fyvie sites. But when I shut down s2/2 link between Culloden and Fyvie, my BGP went to IDLE state.

Culloden(config)#int s2/2
BGP-Neighbor-Adjacency-States: IDLE STATE