Topology

VRRP (Virtual Router Redundancy Protocol) Configuration

First, we will configure the gateway of the network 172.16.1.0/24 on R1 and R2 with the following IP addresses:

• On Router R1: 172.16.1.252/24
• On Router R2: 172.16.1.253/24

Later, we define a VRRP (Virtual Router Redundancy Protocol) VIP: 172.16.1.254 with:

• Router R1 as the Master Router.
• Router R2 as the Backup Router.

R1 Configuration:

conf t
hostname R1
interface Ethernet0/0
 ip address 172.16.1.252 255.255.255.0
 half-duplex
 vrrp 10 ip 172.16.1.254
 vrrp 10 priority 150

R2 Configuration:

conf t
hostname R2
interface Ethernet0/0
 ip address 172.16.1.253 255.255.255.0
 half-duplex
 vrrp 10 ip 172.16.1.254

VRRP Verifications

The Default VRRP priority is 100, so R1 with Priority 150 and R2 with default priority 100.

As a result, R1 will claim the VRRP Master Role:

• Verification on Router R1:

R1#show vrrp brief
Interface          Grp Pri Time  Own Pre State   Master addr     Group addr
Et0/0              10  150 3414       Y  Master  172.16.1.252    172.16.1.254


R1#show vrrp
Ethernet0/0 - Group 10
  State is Master
  Virtual IP address is 172.16.1.254
  Virtual MAC address is 0000.5e00.010a
  Advertisement interval is 1.000 sec
  Preemption enabled
  Priority is 150
  Master Router is 172.16.1.252 (local), priority is 150
  Master Advertisement interval is 1.000 sec
  Master Down interval is 3.414 sec

• Verification on Router R2:

R2#show vrrp brief
Interface          Grp Pri Time  Own Pre State   Master addr     Group addr
Et0/0              10  100 3609       Y  Backup  172.16.1.252    172.16.1.254


R2#show vrrp
Ethernet0/0 - Group 10
  State is Backup
  Virtual IP address is 172.16.1.254
  Virtual MAC address is 0000.5e00.010a
  Advertisement interval is 1.000 sec
  Preemption enabled
  Priority is 100
  Master Router is 172.16.1.252, priority is 150
  Master Advertisement interval is 1.000 sec
  Master Down interval is 3.609 sec (expires in 3.145 sec)

VRRP Wireshark Capture Analysis

VRRP Annoucement packet:

For the Master Backup role election, VRRP Routers on the segment will listen for VRRP announcement packets sent to VRRP Multicast Address 224.0.0.18.

VRRP Packet Flow from PC:

When a ping is started from the PC to VRRP gateway 172.16.1.254 (VIP):

• First of All, an ARP request packet is sent to both R1 and R2.
• Only the Master will respond to this ARP request and associate the VIP with the VRRP MAC address in the ARP reply.

Note: the VRRP MAC of the Groupe is 0000.5e00.010a and it’s only active on the VRRP Master (R1 in our case)

ARP request Wireshark capture on Router R1 interface:

We also can see the ARP request received on R2 Interface:

But the ARP reply is sent only from Router R1 (VRRP Master):

Echo Request to the VRRP IP address:

Note: We can see that the PC device has arp associating the IP 172.16.1.254 to the VRRP MAC 0000.5e00.010a and the Master VRRP will listen (active) to this MAC.