RuggedCom RX1100, RX1000 manual Vrrp Example

Chapter 15 – Configuring VRRP

Each Virtual Router has a user-configured Virtual Router Identifier (VRID) and an Virtual IP address or set of IP addresses on the shared LAN. Hosts on the shared LAN are configured to use these addresses as the default gateway.

One router in the Virtual Router Group will be elected as the Master, all other routers in the group will be Backups.

Each router in the group will run at a specific Priority. The router with the highest priority is elected Master. The value of Priority varies from 1 to 255.

VRRP can also monitor a specified interface and give up control of a VRIP if that interface goes down.

In the following network, host 1 uses a gateway of 1.1.1.253 and host 2 uses a gateway of 1.1.1.252. The 1.1.1.253 gateway is provided by VRID 10. In normal practice router 1 will provide this virtual IP as its priority for VRID 10 is higher than that of router 2. If router 1 becomes inoperative or if its w1ppp link fails, it will relinquish control of VRIP 1.1.1.253 to router 2.

In a similar fashion host 2 can use the VRID 11 gateway address of 1.1.1.252 which will normally be supplied by router 2.

Central Site

Network

w1ppp

	Remote
	Router 1
VRID 10 VRIP = 1.1.1.253		1.1.1.200
VRID 10 Priority = 100
VRID 10 Monitor w1ppp
VRID 11 VRIP = 1.1.1.252
VRID 11 Priority = 50

Switch

w2ppp

Remote

Router 2

1.1.1.201

VRID 10 VRIP = 1.1.1.253 VRID 10 Priority = 50 VRID 11 VRIP = 1.1.1.252 VRID 11 Priority = 100 VRID 10 Monitor w2ppp

Switch

Host 1

Host 2

Figure 136: VRRP Example

In this example traffic from host1 will be sent through router 1 and traffic from host2 through router 2. A failure of either router (or its wan link) will be recovered by the other router.

Note that both routers can always be reached by the hosts at their “real” IP addresses.

Other VRRP parameters are the Advertisement Interval and Gratuitous ARP Delay.

The advertisement interval is the time between which advertisements are sent. A backup router will assume mastership four advertisement intervals after the master fails, so the minimum fail-over time is four seconds. If a monitored interface goes down, a master router will immediately signal an election and allow a backup router to assume mastership.

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