- VRRP stands for Virtual Router Redundancy Protocol.
- It's a protocol to guarantee that the traffic can still flow if a router dies.
- It's a standard from the IETF, it is described in RFC 5798
- The key use case is for an enterprise network, where there is a single point of failure on a site: the Customer Edge router acting as a default gateway. To remove this single point of failure, we use VRRP and put a backup router that takes over the traffic if there is a problem on the master router.
- Having two routers installed, why do we need VRRP? If a dynamic routing protocol is active on the site routers, they will discover the second router a reroute traffic through CE R2 in case of a failure on CE R1. However, it takes time... So VRRP is there to quicken the process.
- How does it work? Logically, the routers form a single virtual router. This means that at layer 2, they bear the same MAC and at layer 3, the same IP. To detect failures quickly, the routers exchange hello messages periodically.
Capture of a VRRP packet through Wireshark (Credit: wikipedia)