Reference Guide

Conguration
VRRP species a master (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 trac.
VRRP packets are transmitted with the virtual router MAC address as the source MAC address. The virtual router MAC address associated
with a virtual router is in format: 00:00:5E:00:01:{VRID} for IPv4 and 00:00:5E:00:02:{VRID} for IPv6. The VRID is the virtual router
identier that allows up to 255 IPv4 VRRP routers and 255 IPv6 VRRP routers on a network. The rst four octets are unquenchable, the
last two octets are 01:{VRID} for IPv4 and 02:{VRID} for IPv6. The nal octet changes depending on the VRRP virtual router identier and
allows for up to 255 VRRP routers on a network.
The example shows a typical network
conguration using VRRP. Instead of conguring 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 congured 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 congured with the virtual router IP address.
If the master router (Router A) becomes unavailable, Router B (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.
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Layer 3