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Defined in RFC 2281, HSRP is a Cisco-proprietary protocol in which routers are put into an HSRP router group. Along with dynamic routing protocols and STP, HSRP is considered a high-availability network service, since all three have an almost immediate cutover to a secondary path when the primary path is unavailable.

One of the routers will be selected as the primary (“Active”, in HSRP terminology), and that primary will handle the routing while the other routers are in standby, ready to handle the load if the primary router becomes unavailable. In this fashion, HSRP ensures a high network uptime, since it routes IP traffic without relying on a single router.

The hosts using HSRP as a gateway don’t know the actual IP or MAC addresses of the routers in the group. They’re communicating with a pseudorouter, a “virtual router” created by the HSRP configuration. This virtual router will have a virtual MAC and IP adddress as well.

The standby routers aren’t just going to be sitting there, though! By configuring multiple HSRP groups on a single interface, HSRP load balancing can be achieved.

Before we get to the more advanced HSRP configuration, we better get a basic one started! We’ll be using a two-router topology here, and keep in mind that one or both of these routers could be multilayer switches as well. For ease of reading, I’m going to refer to them only as routers.

R2 and R3 will both be configured to be in standby group 5. The virtual router will have an IP address of 172.12.23.10 /24. All hosts in VLAN 100 should use this address as their default gateway.

R2(config)#interface ethernet0

R2(config-if)#standby 5 ip 172.12.23.10

R3(config)#interface ethernet0

R3(config-if)#standby 5 ip 172.12.23.10

The show command for HSRP is show standby, and it’s the first command you should run while configuring and troubleshooting HSRP. Let’s run it on both routers and compare results.
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Whether you’re on the road to the CCNA, CCNP, MCSE, or you’re on any other computer certification track, the odds are that sooner or later, you’re going to fail an exam. It’s happened to almost all of us, yours truly included. What you have to keep in mind in these times is that success is not a straight line. You’ve probably seen charts showing the growth of an industry or a business — you know, the ones that go from left to right, and look kind of jagged. The line goes up for a while, then down a bit, then up some more, then down a little.

The key? While every business has its setbacks, the net result is that the line goes up and progress is made. That’s how you want your certification pursuit and your career to go as well – upward!

I’m not asking you to be happy about failing an exam. You’re allowed to get mad for a few minutes, vow to never take another exam again, and be disappointed. What you’re not allowed to do is stay that way.
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