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New Member



I have some questions about HSRP

1# what is HSRP

2# what is the use of HSRP?

3# why do we need it

4# Explain it with examples

any help is appreciated




HSRP is used for redundancy of devices & configured on interface attached to ethernet. In HSRP only one device is active at a time however you can make them work in load-balancing with some modifications.

Lets say you have 2 routers to reach the other end of WAN. Ideally you have gateway address on hosts as router IP address. But when you have 2 routers, which IP will you assign on hosts as default gateway. So HSRP provides a solution by providing a single virtual mac-address to the 2 devices. With this you can create a Virtual IP under each router interface & this virtual IP will be the gateway for all hosts. So when a pc sends pkt to virtual IP, its recvd by the router which is active in configuration & that router fwd the pkt further.

New Member


with hsrp, troubleshooting is made easier by taking out any of the routers providing the WAN link and still have service to the local hosts.

New Member


1# what is HSRP: HSRP is HA solution that uses a virtual mac-address and ip address that each router uses Ex: Router a and Router B are connected to the same subnet lets ay 10.10.10.x where RtrA:.1 and B is .2 the client will use .3 which is the ip address of the Virtual HSRP router.

2# what is the use of HSRP? HSRP again is used in HA environments it is used for redundancy in the event one router link goes down

Ex: HSRP uses multicast address I belive for link detection(hertbeat) every 5 seconds the multicast address polls each router where 1 is tehe active and 2 is the standby if after 3 successfull polls the devuce is considered down and the other(standby assumes the roll of the primary link or the GW (nect hop) for cflient compputers

3# why do we need it: Again this is used for redundancy in HA environments use it at depending on your companies needs

4# Explain it with examples:

Agaim another example is this

typically you have two routers obviouslly on same subnet ex 10.10.10.x network where rtr a is .1 and b is .2 they are considered primary and standby, there is a VR that has an address of .3 and a MAC of 00-00-00-12. Inthe config asll you do is under the Ethernet interface facing lan you add the following


interface eth0/0

ip addr

standby 1 ip addr

standby 1 authent ""

standby 1 preempt 1

standby timers 5 15

again this is every 5 sec and polls 3 consecutive times then the link is down

simply do the same for rtrb with app ipaddress. HTH

New Member


To make more clear

under each router (a,b)


config t

interface ethernet0/0 -> Lan facing interface

ip addr

standby 1 ip address --> IP address of VR

standby 1 preempt

standby 1 priority 100 -> The higher priority in the config is the active router

standby 1 authentication ""

standby 1 timers 5 15

Remember the devices (pri,standby) are polled every 5 sec and after the third attempt the device is ano longer active- until comes back online.

So all you need to do is add the config to (rtrb> and your on your way. HTH