What Is EIGRP?
EIGRP stands for Enhanced Interior Gateway Routing Protocol. It is a Cisco proprietary advanced distance vector routing protocol used for routing decisions within a computer network. EIGRP is designed to efficiently handle large and complex enterprise networks while providing fast convergence and minimal network traffic.
Key Features of EIGRP:
Advanced Distance Vector Protocol: EIGRP is often categorized as an advanced distance vector protocol due to its combination of distance vector and link-state characteristics.
DUAL Algorithm: EIGRP uses the Diffusing Update Algorithm (DUAL) to calculate the shortest path to a destination. DUAL enables rapid convergence by minimizing the time it takes for routers to adapt to changes in the network.
Partial Updates: EIGRP sends partial updates, transmitting only the information that has changed in the network. This results in more efficient use of bandwidth compared to sending complete routing tables.
Support for Multiple Network Layer Protocols: While EIGRP is often associated with IP networks, it is capable of supporting various network layer protocols, making it versatile in mixed protocol environments.
Neighbor Discovery and Maintenance: EIGRP routers establish and maintain neighbor relationships through a process known as the “Hello” protocol. This ensures that routers are aware of each other’s presence and can share routing information.
Variable-Length Subnet Mask (VLSM) Support: EIGRP supports Variable-Length Subnet Masking (VLSM), allowing for more efficient use of IP address space by enabling subnetting within a network.
Rapid Convergence: EIGRP is designed to converge quickly in response to changes in the network, reducing downtime and improving the overall responsiveness of the network.
Now, we look at:
* Configuring EIGRP on a Network
* Redistributing Routes into EIGRP
* Creating a Default Route in EIGRP
Configuring EIGRP on a Network
Lets use the topology below:
To configure EIGRP on a network use the following command:
RO1>enable
RO1#configure terminal
RO1(config router)#eigrp 100
RO1(config-router)#network 192.168.3.0
RO1(config-router)#network 172.16.1.0
RO1(config-router)#no auto-summary
RO1(config-router)#end
From the command above, we used the command router eigrp 100 to turn on the protocol, then we declared all directly connected networks on router RO1.
All other routers on the network must be configured the same way, each router must declare its directly connected network to be seen by other routers on the network, and most importantly, all routers on the same network running EIGRP must be configured with the same process number 100
How to redistribute routes that were learned by the router into the EIGRP routing process;
Use the redistribute command:
Redistributing Routes into EIGRP:
HQ#config t
HQ(config)#ip route 192.168.2.0 255.255.255.0 172.16.1.5
HQ(config)#router eigrp 100
HQ(config-router)#redistribute static
HQ(config-router)#end
HQ#
Setting the properties of the routes that are redistributed from another routing protocol with the default-metric command:
HQ#configure terminal
HQ(config)#router eigrp 100
HQ(config-router)#redistribute rip
HQ(config-router)#default-metric 1000 100 250 100 1500
HQ(config-router)#end
Use the show ip protocols command to view your route redistribution.
How to Create a Default Route in EIGRP.
You want to propagate a default route within EIGRP. Configuring EIGRP to propagate a default route is by simply redistributing a static route to 0.0.0.0/0,
Use the following commands;
HQ#config t
HQ(config)#ip route 0.0.0.0 0.0.0.0 172.16.1.5
HQ(config)#access-list 7 permit 0.0.0.0
HQ(config)#router eigrp 100
HQ(config-router)#redistribute static
HQ(config-router)#distribute-list 7 out static
HQ(config-router)#end
Router1#
If you log on to other routers, you will see that EIGRP is forwarding this route and that it is accepted as a candidate default route. Use the following command to view:
Router2#show ip route 0.0.0.0
EIGRP is commonly used in Cisco environments due to its advanced features and efficient operation. It is particularly well-suited for enterprise networks where rapid convergence and scalability are essential.
How to troubleshoot and verify EIGRP Configuration
How to Configure OSPF on a Cisco Router How to Configure Static Routes
