Dell SmartFabric OS10 User Guide Release 10.5.3

VRRP specifies a master, or active, router that owns the next-hop IP and MAC address for end stations on a LAN. The master router is chosen from the virtual routers by an election process and forwards packets sent to the next-hop IP address. If the master router fails, VRRP begins the election process to choose a new master router which continues routing traffic.

VRRP packets transmit with the virtual router MAC address as the source MAC address. The virtual router MAC address associated with a virtual router is in 00:00:5E:00:01:{VRID} format for IPv4 and 00:00:5E:00:02:{VRID} format for IPv6. The VRID is the virtual router identifier that allows up to 255 IPv4 and IPv6 VRRP routers on a network. The first four octets are unquenchable, the last two octets are 01:{VRID} for IPv4 and 02:{VRID} for IPv6. The final octet changes depending on the VRRP virtual router identifier.

Basic VRRP Configuration

The example shows a typical network configuration using VRRP. Instead of configuring the hosts on network 10.10.10.0 with the IP address of either Router A or Router B as the default router, the default router of all hosts is set to the IP address of the virtual router. When any host on the LAN segment requests Internet access, it sends packets to the IP address of the virtual router.

Router A is configured as the master router with the virtual router IP address and sends any packets addressed to the virtual router to the Internet. Router B is the backup router and is also configured with the virtual router IP address.

If Router A, the master router, becomes unavailable (the connection between the LAN segment and Router A on ethernet 1/1/6 goes down), Router B, the backup router, automatically becomes the master router and responds to packets sent to the virtual IP address. All workstations continue to use the IP address of the virtual router to transmit packets destined to the Internet. Router B receives and forwards packets on interface ethernet 1/1/5. Until Router A resumes operation, VRRP allows Router B to provide uninterrupted service to the users on the LAN segment accessing the Internet.

When the interface that Router A uses to provide gateway services (ethernet 1/1/7) goes down, Router B does not take over automatically. For Router B to become the master router, you must configure interface tracking. When you configure tracking on the interface and the interface goes down, the VRRP group's priority decreases. The lowered priority of the VRRP group triggers an election and Router B becomes the master router. See Interface/object tracking for more information.