All the methods of Default route Injection in EIGRP

Default route injection is a critical technique for directing traffic to a gateway of last resort, commonly used in hub-and-spoke topologies, internet breakouts, and redundant network designs. The specific method you use will depend on the routing protocol.

The default route is used to forward any packet with a destination not found in the routing table, which is why it is also called a gateway of last resort. Also can be used at the end location where there is only one exit path for any destination (internet).

Default routes help in reducing the size of your routing table. It’s the last preferred route in the routing table 

 

There are many ways to inject a default route in EIGRP. In this lab, we test four ways of injecting a default route.

The first method to inject a default route into EIGRP is to configure a static default route pointing to Null0, and then redistribute the default route into EIGRP when redistributing a static, connected, or EIGRP route for another autonomous system; the metric does not need to be assigned. The default route will be an external EIGRP route.

The second method for injecting a default route into EIGRP is to configure a network command with 0.0.0.0. You must have the static default route configured; otherwise, with the network 0.0.0.0, all the existing and future directly connected interfaces will be advertised in the AS. The default route will be an internal EIGRP route. 

The third method for injecting a default route into EIGRP  is to configure the IP summary-address EIGRP interface configuration command. With this command, you are summarizing all the class A, B, and C networks. This means that you are suppressing every route in your routing table, but if you must advertise a specific network, you must leak it. The default route will be an internal EIGRP route.

The fourth method of injecting a default route is to use IP default-network command. 

The goal is to perform all the route injection methods in our topology.

• Configure the topology as per the diagram
• Configure IP addresses as per the topology
• Configure IGP EIGRP AS 65100.
• Advertise directly connected routes
• Configure the first method of route injection (redistribute default route static Null0)
• Configure the Second method of route injection (static and network 0.0.0.0)
• Configure the third method of route injection (only summary address)
• Configure the fourth method of route injection ( IP default-network)

R1(config)#interface serial 2/0
R1(config-if)#ip address 192.168.1.1 255.255.255.0
R1(config-if)#no shutdown
R1(config-if)#exit

R1(config)#interface loopback 1
R1(config-if)#ip address 10.1.1.1 255.0.0.0
R1(config-if)#no shutdown
R1(config-if)#exit

R1(config)#interface fastethernet 0/0
R1(config-if)#ip address 192.168.10.1 255.255.255.0
R1(config-if)#no shutdown
R1(config-if)#exit

R2(config)#interface serial 2/0
R2(config-if)#ip address 192.168.1.2 255.255.255.0
R2(config-if)#no shutdown
R2(config-if)#exit

R2(config)#interface loopback 1
R2(config-if)#ip address 20.1.1.1 255.0.0.0
R2(config-if)#no shutdown
R2(config-if)#exit

R2(config)#interface fastethernet 0/0
R2(config-if)#ip address 192.168.20.1 255.255.255.0
R2(config-if)#no shutdown
R2(config-if)#exit

R1(config)#router eigrp 65100
R1(config-router)#network 192.168.1.0
R1(config-router)#network 10.0.0.0
R1(config-router)#network 192.168.20.0
R1(config-router)#no auto-summary
R1(config-router)#exit

%DUAL-5-NBRCHANGE: EIGRP-IPv4 65100: Neighbor 192.168.1.2 (Serial2/0) is up: new adjacency

R2(config)#router eigrp 65100
R2(config-router)#network 192.168.1.0
R2(config-router)#network 20.0.0.0
R2(config-router)#network 192.168.20.0
R2(config-router)#no auto-summary
R2(config-router)#exit

%DUAL-5-NBRCHANGE: EIGRP-IPv4 65100: Neighbor 192.168.1.1 (Serial2/0) is up: new adjacency

• Configure the first method of route injection (redistribute default route static Null0)

R2(config)#ip route 0.0.0.0 0.0.0.0 null0
R2(config)#router eigrp 65100
R2(config-router)#redistribute static
R2(config-router)#exit

R2(config)#end

R2#show ip route
Codes: L - local, 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, H - NHRP, l - LISP
       + - replicated route, % - next hop override
 
Gateway of last resort is 0.0.0.0 to network 0.0.0.0
 
S*    0.0.0.0/0 is directly connected, Null0
D     10.0.0.0/8 [90/2297856] via 192.168.1.1, 00:07:46, Serial2/0
      20.0.0.0/8 is variably subnetted, 2 subnets, 2 masks
C        20.0.0.0/8 is directly connected, Loopback1
L        20.1.1.1/32 is directly connected, Loopback1
      192.168.1.0/24 is variably subnetted, 2 subnets, 2 masks
C        192.168.1.0/24 is directly connected, Serial2/0
L        192.168.1.2/32 is directly connected, Serial2/0
      192.168.20.0/24 is variably subnetted, 2 subnets, 2 masks
C        192.168.20.0/24 is directly connected, FastEthernet0/0
L        192.168.20.1/32 is directly connected, FastEthernet0/0

R2#show ip eigrp topology 0.0.0.0/0
EIGRP-IPv4 Topology Entry for AS(65100)/ID(20.1.1.1) for 0.0.0.0/0
  State is Passive, Query origin flag is 1, 1 Successor(s), FD is 256
  Descriptor Blocks:
  0.0.0.0, from Rstatic, Send flag is 0x0
      Composite metric is (256/0), route is External
      Vector metric:
        Minimum bandwidth is 10000000 Kbit
        Total delay is 1 microseconds
        Reliability is 0/255
        Load is 0/255
        Minimum MTU is 1500
        Hop count is 0
        Originating router is 20.1.1.1
      External data:
        AS number of route is 0
        External protocol is Static, external metric is 0
        Administrator tag is 0 (0x00000000)
        Exterior flag is set

Configure the Second method of route injection (static and network 0.0.0.0)

R2(config)#router eigrp 65100
R2(config-router)#no redistribute static

R2(config)#ip route 0.0.0.0 0.0.0.0 null0

R2(config)#router eigrp 65100
R2(config-router)#network 0.0.0.0
R2(config-router)#exit

R2#show ip route
Codes: L - local, 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, H - NHRP, l - LISP
       + - replicated route, % - next hop override
 
Gateway of last resort is 0.0.0.0 to network 0.0.0.0
 
S*    0.0.0.0/0 is directly connected, Null0
D     10.0.0.0/8 [90/2297856] via 192.168.1.1, 00:13:35, Serial2/0
      20.0.0.0/8 is variably subnetted, 2 subnets, 2 masks
C        20.0.0.0/8 is directly connected, Loopback1
L        20.1.1.1/32 is directly connected, Loopback1
      192.168.1.0/24 is variably subnetted, 2 subnets, 2 masks
C        192.168.1.0/24 is directly connected, Serial2/0
L        192.168.1.2/32 is directly connected, Serial2/0
      192.168.20.0/24 is variably subnetted, 2 subnets, 2 masks
C        192.168.20.0/24 is directly connected, FastEthernet0/0
L        192.168.20.1/32 is directly connected, FastEthernet0/0

.

R2#show ip eigrp topology 0.0.0.0/0
EIGRP-IPv4 Topology Entry for AS(65100)/ID(20.1.1.1) for 0.0.0.0/0
  State is Passive, Query origin flag is 1, 1 Successor(s), FD is 256
  Descriptor Blocks:
  0.0.0.0, from Rstatic, Send flag is 0x0
      Composite metric is (256/0), route is Internal
      Vector metric:
        Minimum bandwidth is 10000000 Kbit
        Total delay is 1 microseconds
        Reliability is 0/255
        Load is 0/255
        Minimum MTU is 1500
        Hop count is 0
        Originating router is 20.1.1.1
      Exterior flag is set

Configure the third method of route injection (only summary address)

R2(config)#router eigrp 65100
R2(config-router)#no redistribute static
R2(config-router)#no network 0.0.0.0
R2(config-router)#exit

R2(config)#interface serial 2/0
R2(config-if)#ip summary-address eigrp 65100 0.0.0.0 0.0.0.0
R2(config-if)#end

%DUAL-5-NBRCHANGE: EIGRP-IPv4 65100: Neighbor 192.168.1.1 (Serial2/0) is resync: summary configured

R2#show ip route eigrp
Codes: L - local, 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, H - NHRP, l - LISP
       + - replicated route, % - next hop override
 
Gateway of last resort is 0.0.0.0 to network 0.0.0.0
 
D*    0.0.0.0/0 is a summary, 00:00:21, Null0
D     10.0.0.0/8 [90/2297856] via 192.168.1.1, 00:17:20, Serial2/0

R2#show ip eigrp topology 0.0.0.0/0
EIGRP-IPv4 Topology Entry for AS(65100)/ID(20.1.1.1) for 0.0.0.0/0
  State is Passive, Query origin flag is 1, 1 Successor(s), FD is 28160
  Descriptor Blocks:
  0.0.0.0 (Null0), from 0.0.0.0, Send flag is 0x0
      Composite metric is (28160/0), route is Internal
      Vector metric:
        Minimum bandwidth is 100000 Kbit
        Total delay is 100 microseconds
        Reliability is 255/255
        Load is 1/255
        Minimum MTU is 1500
        Hop count is 0
        Originating router is 20.1.1.1