IBM RackSwitch G8000, Application Manual

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RackSwitch G8000: Application Guide
VRRP Overview
In a high-availability network topology, no device can create a single point-of-failure
for the network or force a single point-of-failure to any other part of the network. This
means that your network will remain in service despite the failure of any single
device. To achieve this usually requires redundancy for all vital network
components.
VRRP enables redundant router configurations within a LAN, providing alternate
router paths for a host to eliminate single points-of-failure within a network. Each
participating VRRP-capable routing device is configured with the same virtual router
IPv4 address and ID number. One of the virtual routers is elected as the master,
based on a number of priority criteria, and assumes control of the shared virtual
router IPv4 address. If the master fails, one of the backup virtual routers will take
control of the virtual router IPv4 address and actively process traffic addressed to it.
With VRRP, Virtual Interface Routers (VIR) allow two VRRP routers to share an IP
interface across the routers. VIRs provide a single Destination IPv4 (DIP) address
for upstream routers to reach various servers, and provide a virtual default Gateway
for the servers.
VRRP Components
Each physical router running VRRP is known as a VRRP router .
Virtual Router
Two or more VRRP routers can be configured to form a virtual router (RFC 2338).
Each VRRP router may participate in one or more virtual routers. Each virtual router
consists of a user-configured virtual router identifier (VRID) and an IPv4 address.
Virtual Router MAC Address
The VRID is used to build the virtual router MAC Address . The five highest-order
octets of the virtual router MAC Address are the standard MAC prefix
(00-00-5E-00-01) defined in RFC 2338. The VRID is used to form the lowest-order
octet.
Owners and Renters
Only one of the VRRP routers in a virtual router may be configured as the IPv4
address owner. This router has the virtual router’s IPv4 address as its real interface
address. This router responds to packets addressed to the virtual router’s IPv4
address for ICMP pings, TCP connections, and so on.
There is no requirement for any VRRP router to be the IPv4 address owner. Most
VRRP installations choose not to implement an IPv4 address owner. For the
purposes of this chapter, VRRP routers that are not the IPv4 address owner are
called renters .