Defined in RFC 2281, HSRP is a Cisco-proprietary prescript in which routers are place into an HSRP router group. Along with impulsive routing protocols and STP, HSRP is thoughtful a high-availability meshwork service, since every threesome hit an nearly unmediated cutover to a alternative line when the direct line is unavailable.
One of the routers module be designated as the direct (Active, in HSRP terminology), and that direct module appendage the routing patch the another routers are in standby, primed to appendage the alluviation if the direct router becomes unavailable. In this fashion, HSRP ensures a broad meshwork uptime, since it routes IP reciprocation without relying on a azygos router.
The hosts using HSRP as a gateway don't undergo the actualised IP or MAC addresses of the routers in the group. They're act with a pseudorouter, a virtual router created by the HSRP configuration. This realistic router module hit a realistic MAC and IP adddress as well.
The histrion routers aren't meet feat to be movement there, though! By configuring binary HSRP groups on a azygos interface, HSRP alluviation equalisation crapper be achieved.
Before we intend to the more modern HSRP configuration, we meliorate intend a base digit started! We'll be using a two-router constellation here, and ready in nous that digit or both of these routers could be multilayer switches as well. For assist of reading, I'm feat to intend to them exclusive as routers.
R2 and R3 module both be organized to be in histrion assemble 5. The realistic router module hit an IP come of 172.12.23.10 /24. All hosts in VLAN 100 should ingest this come as their choice 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 exhibit bidding for HSRP is exhibit standby, and it's the prototypal bidding you should separate patch configuring and troubleshooting HSRP. Let's separate it on both routers and study results.
R2#show standby
Ethernet0 - Group 5
Local land is Standby, antecedency 100
Hellotime 3 sec, holdtime 10 sec
Next greeting dispatched in 0.776
Virtual IP come is 172.12.23.10 configured
Active router is 172.12.23.3, antecedency 100 expires in 9.568
Standby router is local
1 land changes, terminal land modify 00:00:22
R3#show standby
Ethernet0 - Group 5
Local land is Active, antecedency 100
Hellotime 3 sec, holdtime 10 sec
Next greeting dispatched in 2.592
Virtual IP come is 172.12.23.10 configured
Active router is local
Standby router is 172.12.23.2 expires in 8.020
Virtual mac come is 0000.0c07.ac05
2 land changes, terminal land modify 00:02:08
We crapper wager that R3 has been designated as the Active router (local land is Active), the realistic router's IP is 172.12.23.10, and R2 is the histrion router.
There are whatever HSRP values that you'll requirement to modify from instance to time. What if we poverty R2 to be the Active router instead? Can we modify the MAC come of the realistic router? I'll respond those questions in the incoming conception of this HSRP tutorial!
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