Chapter 13 – Configuring Dynamic Routing
OSPF And VRRP Example Network
This network consists of three routers connected in a ring with T1/E1 links. Router 1
and 2 and the switched network represent a remote site in which the routers supply a
redundant gateway to the hosts via VRRP and the T1/E1 links supply a redundant
network connection to the rest of the network.
Figure 115: OSPF And VRRP Example
Area And Subnets
As the OSPF design is simple, an area of 0 is used. The three point-to-point T1/E1
links are placed in the area by adding 1.1.1.0/24 to it. Router 1 and 2 will include
their Ethernet links by adding subnet 1.1.2.0/24 to their area descriptions. Router 3
must also include 2.2.2.0/24 in its area description so that its existence is advertised.
The point-to-point T1/E1 interfaces and Ethernet interfaces on Router 1 and 2 must be
made active. The Ethernet interface on Router 3 can be left passive since it does not
participate in OSPF advertisements.
Router 1 and 2 must enable link-detect, to stop advertising 1.1.1.0/24 in the event of a
link failure.
VRRP Operation
Router 1 and 2 have VRRP setup on their Ethernet connection so that they can both
function as the gateway for the clients on their network segment. Normally Router 1
is the VRRP master, and only in case of a link failure to the switch or the router
failing, will Router 2 take over the virtual IP. The virtual IP used as the gateway is
1.1.2.254. Each router also has its own IP on the network so that each can be reached
individually.
RuggedCom 143
Router 2Router 1
w2ppp
w1ppp
1.1.2.1
Router 3
Host 1
VRIP = 1.1.2.254
Priority = 100
VRIP = 1.1.2.254
Priority = 50
Host 2
1.1.2.2
Switch
w2ppp
w1ppp
w1ppp
w2ppp
1.1.1.2
1.1.1.5
1.1.1.6
1.1.1.1
1.1.1.4
1.1.1.3
2.2.2.254
IP: 1.1.2.101
GW: 1.1.2.254
IP: 1.1.2.102
GW: 1.1.2.254
Host 3
IP: 2.2.2.101
GW: 2.2.2.254
Area 0
