Do you know Virtual Router Redundancy Protocol and its configuration

VRRP is an open standard protocol, which is employed to produce redundancy during a network. it's a network layer protocol (protocol number-112).

The number of routers (group members) during an exceedingly group acts as a virtual logical router which is in a position to be the default gateway of all the local hosts. If one router goes down, one in every of the choice group members can occur for the responsibilities for forwarding the traffic.

Some important terms associated with VRRP :

virtual IP address : An IP address is assigned as a virtual IP address from the local subnet which is configured as a default gateway for all the local hosts.
Virtual MAC address : A virtual MAC address is automatically generated by taking the last 8 bytes because the VRRP group number in hexadecimal. In VRRP, Mac address used is 0000.5e00.01xx. Here, xx is that the VRRP group number in hexadecimal.

Master router :

one in every of the VRRP group member is elected as master router which takes up the responsibility of forwarding the local traffic. The router is elected on the premise of priority. If some group member of VRRP group has higher priority than others then it'll be elected as master router. If the priority is same(by default 100) then the router having the foremost effective IP address will become the master router.

Backup routers :

only 1 of the VRRP group member are visiting become the master router while others are visiting be keep a replica routers. just just just in case the master router fails then one in every of the backup routers will become master
router.

Master advertisement timer :

The master router multicast the keep-alive messages at 224.0.0.18 in every 1 second.

Master dead timer :

The time within which the backup router will take up the responsibilities of Master router if the master advertisement message isn't received. It is, by default, 3.69 seconds.

Prempt :

it's a state during which one in every of the backup routers become the master router (when the master router goes down). Also, when the master router comes up again, it'll become the master router as it’s priority continues to be higher.

Object tracking :

The VRRP object tracking provides some way within which the sole router will become the master router. the present master router continuously polls the tracked object state (such as line protocol is up or down). Suppose if the master router line protocol is down then the priority of backup router are increased dynamically i.e it'll become the master router.

Authentication :

VRRP supports 3 sorts of authentication –

1. No authentication
2. Plain text authentication
3. MD5 authentication


Configuration:

In above given topology, there are 2-routers named R1 and R2, where R1 fa 0/0 ip address is 10.100.1.1/24 and R2 fa0/0 ip address is 10.1.1.2/24.

Assigning IP address to router R1 :

r1# int fa0/0
r1# ip add 10.100.1.1 255.255.255.0
Assigning IP address to router r2.

r2# int fa0/0
r2# ip address 10.100.1.2 255.255.255.0

OK fine hence now, let us providing a actual virtual IP address(10.100.1.100), group name VRRP_NETWY, group number 10 and priority 110. One more thing, here preempt has been enabled by default

Example: In case the master router goes down then after the backup router automatically becomes the master router.

r1# int fa0/0
r1# vrrp 10 ip 10.100.1.100
r1# vrrp 10 name VRRP_NETWY
r1# vrrp 10 priority 110
Now, provide virtual IP address(10.100.1.100), group name VRRP_NETWY and priority 100. Also, group number 10 is assigned.

r2# int fa0/0
r2# vrrp 10 ip 10.100.1.100
r2# vrrp 10 name VRRP_NETWY
r2# vrrp 10 priority 100

Note : As provided priority 110 to r1, therefore, it'll become the master router.