3Com 4007, Implementation Manual, Page: 404 / 684

404 C
HAPTER
17: V
IRTUAL
R
OUTER
R
EDUNDANCY
P
ROTOCOL
(VRRP)
■
A Backup router monitors the availability and state of the Master, and:
■
Does not respond to ARP requests for the IP address or addresses
associated with the virtual router.
■
Discards packets that have a destination Link Layer MAC address
that matches the virtual router MAC address.
■
Does not accept packets addressed to the IP address or addresses
associated with the virtual router
■
Hosts obtain the virtual router’s MAC address by means of an ARP
broadcast.
■
VRRP is not a routing protocol, and its usefulness is only as good as
the design of the network upon which it is implemented. Good
network design is critical in ensuring the success of router redundancy.
■
The virtual routers must be on the same VLAN.
■
VRRP supports Proxy ARP; the virtual router uses the virtual router
MAC address in Proxy ARP replies.
■
VRRP supports Fiber Distributed Data Interface (FDDI) and Ethernet
■
Consider using VRRP in conjunction with port-based routing to
provide router redundancy on your campus backbone. See Chapter 16
for an example of port-based routing on a campus backbone.
VRRP and Other
Networking
Operations
Read this section for information about how VRRP interacts with other
networking functions, including:
■
Spanning Tree Protocol (STP)
■
Dynamic routing protocols:
■
Routing Information Protocol (RIP)
■
Routing Information Protocol version 2 (RIP-2)
■
Open Shortest Path First (OSPF)
■
IP Multicast
■
ICMP Redirect
■
Quality of Service (QoS)