VRRP Overview
Configuring VRRP
page 22-8
OmniSwitch AOS Release 7 Network Configuration Guide
June 2013
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, as the MAC address in ARP replies sent by VRRPv2, and
as the MAC address in neighbor advertisements sent by VRRPv3 (instead of the MAC address for the
physical VRRP router).
The VRRPv2 (IPv4) address has the following format:
00-00-5E-00-01-[virtual router ID]
The VRRPv3 (IPv6) address has the following format:
00-00-5E-00-01-[virtual router ID]
Note.
By default, in AOS Release 7.2.1, packets that originate from a switch with an address assigned to a
VRRPv3 virtual router will use the physical MAC as their source, not the VRRP virtual MAC. The
ipv6
virtual-source-mac
command can be used to modify this behavior resulting in the VRRP virtual MAC
being used as the source. This command has no effect on VRRP advertisements, which will always be sent
using the VRRP virtual MAC as the source.
In AOS Release 7.1.1, packets that originate from a switch with an address assigned to a VRRPv3 virtual
router will always use the VRRP virtual MAC.
ARP Requests
Each virtual router has a single well-known MAC address, which is used as the MAC address in ARP
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 are delayed at
system boot until both the
IP
address and the virtual router MAC address are configured.
If an interface IP address is shared by a virtual router, the routing mechanism does not send a gratuitous
ARP for the IP address (since the virtual router will send a gratuitous ARP). This prevents traffic from
being forwarded to the router before the routing tables are stabilized.
ICMP Redirects
ICMP redirects are not sent out over VRRP interfaces.