Vrrp Mac Addresses; Arp Requests; Icmp Redirects - Alcatel OmniSwitch 6624 Network Configuration Manual

VRRP Overview
If backup routers are configured with priority values that are close in value, there may be a timing conflict,
and the first backup to take over may not be the one with the highest priority; a backup with a higher prior-
ity will then preempt the new master. The virtual router may be configured to prohibit any preemption
attempts, except by the IP address owner. An IP address owner, if it is available, will always become
master of any virtual router associated with its IP addresses.
Note. Duplicate IP address/MAC address messages may display when a backup takes over for a master,
depending on the timing of the takeover and the configured advertisement interval. This is particularly true
if more than one backup is configured.

VRRP MAC Addresses

Each virtual router has a single well-known MAC address, which is used as the source in all periodic
VRRP advertisements sent by the master router, any other packets originating from the master router, and
as the MAC address in ARP replies (instead of a VRRP router's physical MAC address). The address has
the following format:
00-00-5E-00-01-[virtual router ID]
This mapping provides for up to eight virtual routers on an OmniSwitch.

ARP Requests

Each virtual router has a single well-known MAC address, which is used as the MAC address in ARP
replies instead of a VRRP router's physical MAC address. When an end host sends an ARP request to the
master router's IP address, the master router responds to the ARP request using the virtual router MAC
address. If a backup router takes over for the master, and an end host sends an ARP request, the backup
will reply to the request using the virtual router MAC address.
Gratuitous ARP requests for the virtual router IP address or MAC address are broadcast when the
OmniSwitch becomes the master router. For VRRP interfaces, gratuitous ARP requests/responses are
delayed at system boot until both the

ICMP Redirects

ICMP redirects are not sent out over VRRP interfaces.
page 16-6
address and the virtual router MAC address are configured.
IP
OmniSwitch 6624/6648 Network Configuration Guide
Configuring VRRP
April 2004