Virtual Router Redundancy Protocol (VRRP)
VRRP provides redundancy in a network and is an open standard protocol. It is a network layer protocol. A virtual logical router acts as the default gateway for all the local hosts. This virtual router is a group of a number of physical routers. If one router goes down, other members can be used to serve the responsibility of forwarding the traffic.
Some important points related to VRRP:
| 1 | Virtual IP address: The IP address used as default gateway is configured for all the local hosts which is a virtual IP address from the local subnet |
| 2 | Virtual MAC address: The last 8 bytes of the VRRP group number in hexadecimal are used to generate a Virtual MAC address. In VRRP, Mac address used is 0000.5e00.01xx. Here, VRRP group number is shown in Hexadecimal i.e. xx. |
| 3 | Master router: The responsibility of forwarding the local traffic is of the master router that is elected from the VRRP group. On the basis of priority the router is elected. The group member with higher priority is elected as the master router. Firstly, the priority is checked if it is same (by default 100) then the router having the highest IP address will become the master router. |
| 4 | Backup routers: All the routers in the VRRP group are backup routers except for one master router. In case of failure of the master router one router from the backup routers will become as a master router. |
| 5 | Master advertisement timer: The keep-alive messages are multicast in every 1 second at 224.0.0.18 by the master router. |
| 6 | Master dead timer: If the master router fails to send master advertisement message then the backup router will take up the responsibilities in this time. It is, by default, 3.69 seconds. |
| 7 | Pre-empt: It is a state in which one of the backup routers becomes the master router (when the master router goes down). The priority of the master router which has gone down is still higher. So when the master router comes up again, it will again become the master router. |
| 8 | Object tracking: The VRRP object tracking provides a way in which the best router will become the master router. The current 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 will be increased dynamically i.e. it will become the master router. |
| 9 | Authentication: VRRP supports 3 types of authentication – 1. No authentication 2. Plain text authentication 3. MD5 authentication. |
The above mentioned features are offered and supported by VCL-MX-50xx family of IP/MPLS Routers.
Reference:
Geeks-For-Geeks. (2022). Introduction of Virtual Router Redundancy Protocol (VRRP) and its configuration.