Dell PowerConnect B-RX Configuration Manual page 528

17
Overview of VRRP
As shown in this example, Host1 uses 192.53.5.1 on Router1 as the host's default gateway out of
the subnet. If this interface goes down, Host1 is cut off from the rest of the network. Router1 is
thus a single point of failure for Host1's access to other networks.
If Router1 fails, you could configure Host1 to use Router2. Configuring one host with a different
default gateway might not require too much extra administration. However, consider a more
realistic network with dozens or even hundreds of hosts per subnet; reconfiguring the default
gateways for all the hosts is impractical. It is much simpler to configure a VRRP virtual router on
Router1 and Router2 to provide a redundant path for the hosts. If VRRP is enabled as in
Router 2 provides the default gateway out of the subnet if Router 1 fails.
FIGURE 85
With VRRP, you configure virtual routers that span across the physical routers. A virtual router acts
as a default router for hosts on a shared LAN. For example,
configured identified as VRID1.This virtual router ID is associated with Router 1 and Router 2.
Since there are more than one IP addresses configured on Router 1 and Router 2, one of the
physical addresses is assigned to the virtual router. For example, in
192.53.5.1, the IP address assigned to Router 1's interface 1/6, is assigned as the IP address of
virtual router VRID1. Router 1 becomes the Owner of the virtual router VRID1 and is the router that
responds to packets addresses to any of the IP addresses in virtual router VRID1.
In addition, one router in the virtual router is elected as the Master router. Other routers act as
backups. The Master router is the one that forwards packets sent to the IP addresses in the virtual
router and answers ARP requests for these IP addresses. The Backup router takes over for the
Master router when the Master router fails.
452
Router1 and Router2 are configured as a VRRP virtual router to provide redundant
network access for Host1
Internet
or
enterprise Intranet
e 2/4
Router1
VRID1
Router1 = Master
e 1/6 192.53.5.1
IP address = 192.53.5.1
MAC address = 00-00-5E-00-01-01
Owner
Priority = 255
Internet
or
enterprise Intranet
e 3/2
Router2
192.53.5.3 e 1/5
Host1
Default Gateway
192.53.5.1
Figure 85
BigIron RX Series Configuration Guide
Figure
VRID1
Router2 = Backup
IP address = 192.53.5.1
MAC address = 00-00-5E-00-01-01
Priority = 100
has one virtual router
Figure 85, IP address
53-1002253-01
85,