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Configuring EIGRP Stub in Cisco

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Pre-requisites: EIGRP Implementation in Cisco, EIGRP FUNDAMENTALS.

EIGRP stub area routing is a feature specifically designed to improve network scalability and stability. It is most commonly used in hub-and-spoke networks and is configured only on spoke routers in the topology.

The EIGRP stub area routing feature provides many advantages when implemented in a hub-and-spoke network as follows:

  1. It prevents suboptimal EIGRP routing from occurring within the network.
  2. This prevents stub routers with low-speed links from being used as transit routers within the hub-and-spoke network.
  3. It significantly limits the number of query packets and the depth of their propagation, resulting in faster convergence of the EIGRP network and avoiding the stuck-in-active (SIA) states.

EIGRP Stub Network Configuration Command :

A stub router within a hub-and-spoke network advertises only a subset of its EIGRP-enabled networks to its neighbors. The subset can be configured with the eigrp stub <keyword> subcommand in the router configuration mode with the following keywords:

Keyword

Description

connected Allows the stub router to advertise directly connected networks
leak-map Allows the stub router to advertise only route prefixes that match a specific IP prefix-list.
receive-only The stub router will not advertise any network
redistributed Allows the stub router to advertise redistributed routes
static Allows the stub router to advertise static routes (you have to redistribute
them).
summary Allows the stub router to advertise summary routes

 

Note: If no keyword is used with the eigrp stub subcommand which is the default stub configuration as a The command additional keyword is not specified, the default stub will send both connected and summary routes and receive all routes from upstream neighbors.

Syntax:

eigrp stub <receive-only | connected | static | summary | redistribute | leak-map>

The command is executed in the EIGRP routing process configuration mode to specify a router as a stub route.

Configuring EIGRP Stub network:

Step 1: Create the 3 router topologies in GNS3 as shown in the image below:

Configuring EIGRP Stub network

 

Step 2: Configure the IPv4 address on the physical interface of the routers:

On R1:

R1(config)#int f0/0
R1(config-if)#ip address 12.0.0.1 255.255.255.0
R1(config-if)#no shutdown

On R2:

R2(config)#int f0/0
R2(config-if)#ip address 12.0.0.2 255.255.255.0
R2(config-if)#no shutdown
R2(config-if)#int f1/0
R2(config-if)#ip address 23.0.0.1 255.255.255.0
R2(config-if)#no shutdown

On R3:

R3(config)#int f0/0
R3(config-if)#ip address 23.0.0.2 255.255.255.0
R3(config-if)#no shutdown

Step 3: Configure a loopback interface on R1 with an IPv4 address :

R1(config)#int loopback0
R1(config-if)#ip address 1.1.1.1 255.255.255.255
R1(config-if)#exit

Step 4: Configure a loopback interface on R3 with an IPv4 address :

R3(config)#int loopback0
R3(config-if)#ip address 3.3.3.3 255.255.255.255
R3(config-if)#exit

Step 5: Configuring the EIGRP process on both routers with the command router eigrp <1-65535  Autonomous system number> :

R1(config)#router eigrp 10
R1(config-router)#network 12.0.0.0
R1(config-router)#network 1.0.0.0
R2(config)#router eigrp 10
R2(config-router)#network 12.0.0.0
R2(config-router)#network 23.0.0.0
R3(config)#router eigrp 10
R3(config-router)#network 23.0.0.0
R3(config-router)#network 3.0.0.0

Step 6: Checking the IPv4 routing table on the routers and seeing the EIGRP route entry :

R1#show ip route
Configuring EIGRP Stub network

 

R2#show ip route
Configuring EIGRP Stub network

 

R3#show ip route
Configuring EIGRP Stub network

 

Checking Connectivity: 

Ping R3’s loopback interface from R1:

Checking connectivity

 

Ping R1’s loopback interface from R3:

 

 

 

 

Step 7: Configuring R2 as a stub router, R2 will send both connected and summary routes and receive all routes from upstream neighbors:

R2(config)#router eigrp 10
R2(config-router)#eigrp stub 

 

Step 8: Checking the IPv4 routing table on the routers and seeing the changes in EIGRP route entry :

R1#show ip route
  • No EIGRP route entry to the network 3.0.0.0 configured on R3’s loopback interface.

 

R2#show ip route
  • No changes in the R2 IPv4 routing table.

 

R3#show ip route
  • No EIGRP route entry to the network 1.0.0.0 configured on R1’s loopback interface.

 

Checking connectivity: 

 

 

 



Last Updated : 17 Dec, 2022
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