Configuring EIGRP Stub in Cisco
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:
- It prevents suboptimal EIGRP routing from occurring within the network.
- This prevents stub routers with low-speed links from being used as transit routers within the hub-and-spoke network.
- 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:
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
R2#show ip route
R3#show ip route
Checking Connectivity
Ping R3’s loopback interface from R1:
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.
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