EIGRP Named Mode

Description

In this guide, we will cover configuring a simple EIGRP topology using "named" mode.

EIGRP Named Mode Lab Diagram

Configuration

First, let's see from show commands and our network diagram what networks we need to advertise to our neighbor

1. R1 - 192.168.10.0/24, 192.168.20.0/24, 24.0.0.0/31
2. R2 - 10.10.10.0/24, 10.10.20.0/24, 24.0.0.0/31

Now let's configure EIGRP named mode.

CLI Configuration

R1(config)#router eigrp TEST # This command will create a local EIGRP named instance

R1(config-router)#address-family ipv4 unicast autonomous-system 5 # This command will create an IPv4 EIGRP routing domain. This is how you set the AS number for named EIGRP configuration

R1(config-router-af)#network [network-address] [wildcard-mask] # The network command will enable all interfaces that match the network address you input to start sending and receiving EIGRP messages.

The full configuration is pictured below.

R1 EIGRP Configuration

R2 EIGRP Configuration

Verification

To verify that your EIGRP topology is fully converged, we have a LOT of show commands. I will cover the ones I have used the most in day-to-day troubleshooting on an EIGRP domain.

R1#show ip eigrp neighbors # This command will verify that you and your neighbor router have exchanged EIGRP hello packets and have agreed to become neighbors

show ip eigrp neighbors command output

R1#show ip eigrp topology # This command will verify that the EIGRP topology has been built. It will also show the feasible successors and the successor routes. This command will show the reported distance and feasible distance of the routes.

show ip eigrp topology command output

R1#show ip eigrp topology all-links # This command will show you successor routes, feasible successor routes, and even the routes that don't meet the feasibility condition.

R1#show ip protocols # This command will show you all the routing protocols enabled on your routers and the networks they are advertising.

show ip protocols command output

R1show run | section router eigrp # This command will show us the running configuration for just our EIGRP configuration.

show run | section router eigrp command output

R1#show ip route eigrp # This command will show us just the EIGRP learned routes on the global routing table.

show ip route eigrp command output

R1#show ip eigrp interfaces # This command will show us all the interfaces that are participating in EIGRP

show ip eigrp interfaces command output

Wireshark

Now let's look at a packet capture of the EIGRP process. We will take a dive into a hello packet and an update packet.

1. This image shows us the entire process, from EIGRP hellos to EIGRP updates and EIGRP acknowledgments.

Full EIGRP Process for two neighbors

2. In This image, we will look inside the EIGRP Hello Packet. Inside the EIGRP hello header, we can see the opcode (5), which means this is Hello packets, Parameters (K Values which have to match), and the Autonomous System Number, which also has to match on both sides.

EIGRP Hello Packet Capture

3. In this image, we will look inside an EIGRP Update Packet. In this packet, we see R1 is sending the known networks to R2. R2 will take this update, place these networks into the topology table, run the DUAL algorithm, and place these networks into the global routing table.

EIGRP Update Packet

Conclusion

As we can see in the configurations above, configuring EIGRP and getting our routers to dynamically share routes is relatively simple and easy. Now when we get to larger scale networks and tuning our EIGRP, that's a different story. In the upcoming guides, we will go over additional EIGRP configurations like summarization, passive interface, authentication, stub routing, default-information originate, leak-maps, distribute-lists, load-balancing, and offset lists.