Configuring Default route in EIGRP:

Configuring Default route in EIGRP:

   ·         There are 3 ways to advertise a default route in EIGRP

   1.  IP default-network

2.  Redistribute static default route

3.  Summary route

 

·         Let me take a small topology to configure default route in RIP

 

R1------S1/0-------------s1/0----R2----s1/1--------------s1/1------R3

 

10.1.12.1--------------10.1.12.2-----11.1.23.2--------------11.1.23.3

 

·         Let me configure all these options in R2, so that it will generate default route towards R1

 

R1(config)#do show run | sec router

router eigrp 100

 network 10.1.12.1 0.0.0.0

 no auto-summary

R1(config)#

 

R2(config-router)#do show run | sec router

router eigrp 100

 network 10.1.12.2 0.0.0.0

 no auto-summary

R2(config-router)#

 

R1(config)#do 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 not set

 

     10.0.0.0/24 is subnetted, 1 subnets

C       10.1.12.0 is directly connected, Serial1/0

R1(config)#

 

R2(config-router)#do 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 not set

 

     10.0.0.0/24 is subnetted, 1 subnets

C       10.1.12.0 is directly connected, Serial1/0

     11.0.0.0/24 is subnetted, 1 subnets

C       11.1.23.0 is directly connected, Serial1/1

R2(config-router)#

 

Observation:

·         EIGRP is configured between R1 and R2

·         No default route or static router is configured in R1 or in R2

 

1.  Let me configure redistribute static option:

 

R2(config)#ip route 0.0.0.0 0.0.0.0 ser1/1

R2(config)#router eigrp 100

R2(config-router)#redistribute static metric 1 1 1 1 1

R2(config-router)#

 

R2(config-router)#do 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 0.0.0.0 to network 0.0.0.0

 

     10.0.0.0/24 is subnetted, 1 subnets

C       10.1.12.0 is directly connected, Serial1/0

     11.0.0.0/24 is subnetted, 1 subnets

C       11.1.23.0 is directly connected, Serial1/1

S*   0.0.0.0/0 is directly connected, Serial1/1

R2(config-router)#

 

R1(config)#do 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 10.1.12.2 to network 0.0.0.0

 

     10.0.0.0/24 is subnetted, 1 subnets

C       10.1.12.0 is directly connected, Serial1/0

D*EX 0.0.0.0/0 [170/2560512256] via 10.1.12.2, 00:00:53, Serial1/0

R1(config)#

 

Observation:

·         R1 has received default-route from R2

 

2.  Let me configure ip default-network option now:

 

R2(config-router)#

R2(config-router)#no redistribute static metric 1 1 1 1 1

R2(config-router)#no ip route 0.0.0.0 0.0.0.0 ser1/1

R2(config)#ip default-network 11.0.0.0

R2(config)#

 

R1(config)#do 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 not set

 

     10.0.0.0/24 is subnetted, 1 subnets

C       10.1.12.0 is directly connected, Serial1/0

R1(config)#

 

Observation:

·         R1 still don’t see the default route.

·         This is because R2 should have 11.0.0.0 in its EIGRP routing table, then only it will advertise this as a default route

 

R2(config)#router eigrp 100

R2(config-router)#network 11.0.0.0

R2(config-router)#

 

R1(config)#do 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 not set

 

     10.0.0.0/24 is subnetted, 1 subnets

C       10.1.12.0 is directly connected, Serial1/0

     11.0.0.0/24 is subnetted, 1 subnets

D       11.1.23.0 [90/2681856] via 10.1.12.2, 00:00:56, Serial1/0

R1(config)#

 

Observation:

·         R1 has 11.1.23.0 route in its routing table, but still don’t see it as a default route.

·         This is because auto-summary option is disabled in R2.

R2(config-router)#auto-summary

R2(config-router)#

*Mar  1 02:35:35.567: %DUAL-5-NBRCHANGE: IP-EIGRP(0) 100: Neighbor 10.1.12.1 (Serial1/0) is resync: summary configured

R2(config-router)#

 

R1(config)#

*Mar  1 02:35:35.523: %DUAL-5-NBRCHANGE: IP-EIGRP(0) 100: Neighbor 10.1.12.2 (Serial1/0) is resync: peer graceful-restart

R1(config)#

 

R1(config)#do 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 10.1.12.2 to network 11.0.0.0

 

     10.0.0.0/24 is subnetted, 1 subnets

C       10.1.12.0 is directly connected, Serial1/0

D*   11.0.0.0/8 [90/2681856] via 10.1.12.2, 00:00:35, Serial1/0

R1(config)#

 

R2(config-router)#do 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 0.0.0.0 to network 11.0.0.0

 

     10.0.0.0/8 is variably subnetted, 2 subnets, 2 masks

C       10.1.12.0/24 is directly connected, Serial1/0

D       10.0.0.0/8 is a summary, 00:01:00, Null0

 *   11.0.0.0/8 is variably subnetted, 2 subnets, 2 masks

D*      11.0.0.0/8 is a summary, 00:01:00, Null0

C       11.1.23.0/24 is directly connected, Serial1/1

R2(config-router)#

 

Observation:

·         R1 now has a default-route from R2.

·         This is because auto-summary option is enabled in R2.

·         Even R2 flagged this route as a default-route in its routing table.

 

3.  Let me configure summary-route option now:

 

R2(config-router)#no auto-summary

R2(config-router)#

*Mar  1 02:57:11.647: %DUAL-5-NBRCHANGE: IP-EIGRP(0) 100: Neighbor 10.1.12.1 (Serial1/0) is resync: summary configured

R2(config-router)#no network 11.0.0.0

R2(config-router)#no ip default-network 11.0.0.0

R2(config)#

 

R2(config)#int ser1/0

R2(config-if)#ip summary-address eigrp 100 0.0.0.0 0.0.0.0

R2(config-if)#

 

R1(config)#do 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 10.1.12.2 to network 0.0.0.0

 

     10.0.0.0/24 is subnetted, 1 subnets

C       10.1.12.0 is directly connected, Serial1/0

D*   0.0.0.0/0 [90/2681856] via 10.1.12.2, 00:00:02, Serial1/0

R1(config)#

 

R2(config-if)#do 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 0.0.0.0 to network 0.0.0.0

 

     10.0.0.0/24 is subnetted, 1 subnets

C       10.1.12.0 is directly connected, Serial1/0

     11.0.0.0/24 is subnetted, 1 subnets

C       11.1.23.0 is directly connected, Serial1/1

D*   0.0.0.0/0 is a summary, 00:02:03, Null0

R2(config-if)#

 

Observation:

·         R1 has a default route now