How to generate default routes in EIGRP

There are several ways to generate a default route as an EIGRP route and advertise it to other routers, as follows.

  • Redistribute the static default route to EIGRP
  • Route summarization
  • ip default-network command

In the following sections, we will explain the configuration example of redistributing the static default route.

Redistribute the static default route to EIGRP

【Network diagram】

Fig. Network diagram
Fig. Network diagram

【Condition】

  • Allow R2 to advertise the default route to R3 via EIGRP to ensure connectivity for all interfaces.
  • The default route generation is done by static route redistribution.

【Initial configuration】

R1 initial configuration

interface Loopback0
 ip address 172.16.2.1 255.255.255.0 secondary
 ip address 172.16.1.1 255.255.255.0
!
interface Ethernet0/0
 ip address 192.168.12.1 255.255.255.0
!
ip route 192.168.0.0 255.255.0.0 192.168.12.2

R2 initial configuration

interface Ethernet0/0
 ip address 192.168.12.2 255.255.255.0
!
interface Ethernet0/1
 ip address 192.168.23.2 255.255.255.0
!
router eigrp 100
 network 192.168.23.0
 no auto-summary

R3 initial configuration

interface Loopback0
 ip address 192.168.3.3 255.255.255.0
!
interface Ethernet0/0
 ip address 192.168.23.3 255.255.255.0
!
router eigrp 100
 network 192.168.3.0
 network 192.168.23.0
 no auto-summary

【Step1:Configure static default route】

Configure the default route as a static route on R2.

R2 Configure static default route

ip route 0.0.0.0 0.0.0.0 192.168.12.1

【Step2:Redistribute static routes to EIGRP】

Redistribute the static route to EIGRP on R2 in order to make the default route configured in Step 1 as the EIGRP route.

R2 Redistribute static routes to EIGRP

router eigrp 100
 redistribute static

When the redistribution source is static and connected, there is no need to specify a seed metric.

【Step3:Verifying the default route】

Verify that the default route is registered as an EIGRP route in the routing table of R3.

R3

R3#show ip route 
Codes: C - connected, S - static, R - RIP, M - mobile, B - BGP
       D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area 
       N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
       E1 - OSPF external type 1, E2 - OSPF external type 2
       i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2
       ia - IS-IS inter area, * - candidate default, U - per-user static route
       o - ODR, P - periodic downloaded static route

Gateway of last resort is 192.168.23.2 to network 0.0.0.0

C    192.168.23.0/24 is directly connected, Ethernet0/0
C    192.168.3.0/24 is directly connected, Loopback0
D*EX 0.0.0.0/0 [170/307200] via 192.168.23.2, 00:00:03, Ethernet0/0

【Step4:Vefifying communication】

Execute a ping from R3 to R1 to verify that communication is possible.

R3

R3#ping 172.16.1.1 source 192.168.3.3

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 172.16.1.1, timeout is 2 seconds:
Packet sent with a source address of 192.168.3.3 
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 8/12/20 ms
R3#ping 172.16.2.1 source 192.168.3.3

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 172.16.2.1, timeout is 2 seconds:
Packet sent with a source address of 192.168.3.3 
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 1/10/20 ms

How the EIGRP works