In this lesson we’ll take a look how we can configure a default route in EIGRP. Basically there are two methods how you can do this:
- Create a static route and advertise it into EIGRP.
- Flag an EIGRP route as the default network.
We will take a look at both methods. This is the topology we will use:
R1 and R2 are configured for EIGRP, R2 is connected to an ISP router. Behind the ISP is network 18.104.22.168 /24 that we can use to test our default route.
Here’s the configuration of R1 and R2:
R1#show run | section eigrp router eigrp 12 network 192.168.12.0 no auto-summary
R2#show run | section eigrp router eigrp 12 network 192.168.12.0 no auto-summary
Nothing special, R1 and R2 are neighbors but that’s it.
Static Default Route
Let’s start with the first option, the static default route:
R2(config)#ip route 0.0.0.0 0.0.0.0 FastEthernet 0/1 R2(config)#router eigrp 12 R2(config-router)#network 0.0.0.0
We configure the default route on R2 with FastEthernet 0/1 as the exit interface. In EIGRP we can use the network 0.0.0.0 command to advertise this. This might sound strange but it works, normally you can only use the network command to advertise networks on interfaces but EIGRP wil make an exception for this default route.
Let’s see what R1 thinks of this:
R1#show ip route eigrp | begin 0.0.0.0 Gateway of last resort is 192.168.12.2 to network 0.0.0.0 D* 0.0.0.0/0 [90/30720] via 192.168.12.2, 00:01:11, FastEthernet0/0
R1 has learned the default route.
Want to take a look for yourself? Here you will find the final configuration of each device.
hostname ISP ! interface FastEthernet0/0 ip address 192.168.23.3 255.255.255.0 ! interface Loopback0 ip address 22.214.171.124 255.255.255.0 ! ip route 192.168.12.0 255.255.255.0 192.168.23.2 ! end
hostname R1 ! interface FastEthernet0/0 ip address 192.168.12.1 255.255.255.0 ! router eigrp 12 no auto-summary network 192.168.12.0 ! end
hostname R2 ! interface FastEthernet0/1 ip address 192.168.23.2 255.255.255.0 ! interface FastEthernet1/0 ip address 192.168.12.2 255.255.255.0 ! ip route 0.0.0.0 0.0.0.0 FastEthernet0/1 ! router eigrp 12 no auto-summary network 192.168.12.0 network 0.0.0.0 ! end
Let’s look at the other method. Let’s get rid of the default route now so we can try the other method:
R2(config)#router eigrp 12 R2(config-router)#no network 0.0.0.0 R2(config)#no ip route 0.0.0.0 0.0.0.0 FastEthernet 0/1
There we go…let’s continue!
IP Default Network
This one is a bit tricky, we can use the ip default-network command to tell other EIGRP routers that this is a network of “last resort”. This means that they can use it as a default route. We will advertise the network between R2 and ISP in EIGRP and configure it as the “default network”: