Why we use vrrp

The primary and backup members of a Virtual Chassis configuration compose a single host. In a VRRP topology, one host operates as the primary routing platform and another operates as the backup routing platform, as shown in Figure 3.

See also draft-ietf-vrrp-unified-mib This support is achieved through the backward compatibility options in RFC On EX and EX switches, the VRRP protocol must be configured with a Hello interval of 2 seconds or more with dead interval not less than 6 seconds to prevent flaps during CPU intensive operations events such as routing engine switchover, interface flaps, and exhaustive data collection from the packet forwarding engine. Figure 1 illustrates a basic VRRP topology.

The IP address of this virtual router is Clients 1 through 3 are configured with the default gateway IP address of As the primary router, Router A forwards packets sent to its IP address. If the primary virtual router fails, the router configured with the higher priority becomes the primary virtual router and provides uninterrupted service for the LAN hosts.

When Router A recovers, it becomes the primary virtual router again. In some cases, during an inherit session, there is a small time frame during which two routers are in Primary-Primary state. So, it takes the routers up to seconds to recover after moving to Primary-Backup state from Primary-Primary state. For example, if you have computers then you configure 50 of them to use I just checked my and this is the IOS image I am using:. Ask a question or join the discussion by visiting our Community Forum.

Skip to content Search for: Search. Multicast address Hello timer 1 second, hold time 3 seconds. Explained As Simple As Possible. Full Access to our Lessons. The information in this document was created from the devices in a specific lab environment. All of the devices used in this document started with a cleared default configuration. If your network is live, make sure that you understand the potential impact of any command. Refer to Cisco Technical Tips Conventions for more information on document conventions.

The responding Backup assumes the role of Primary. Note: VRRP enables redundancy for tunnel connections only. Therefore, if a VRRP failover occurs, the backup only listens to tunnel protocols and traffic. Pinging the VPN Concentrator does not work. Participating VPN Concentrators must have identical configurations. The virtual addresses configured for VRRP must match those configured on the interface addresses of the Primary. VRRP is configured on the public and private interfaces in this configuration.

If the Primary fails, the Backup begins to service traffic formerly handled by the Primary.