Building an Enterprise Network: Configuring EIGRP for Seamless Multi-Site Connectivity
In the previous post, we designed and implemented the foundational setup of our enterprise network. Now, we'll take a step further by configuring EIGRP (Enhanced Interior Gateway Routing Protocol) to dynamically manage routing between our three sites: London, Manchester, and Glasgow. This will eliminate the need for static routes and ensure seamless connectivity between all network devices.
If you have not seen the previous post, then you can find it below.
Dylan Hughes
- Understanding EIGRP
EIGRP is a Cisco-proprietary dynamic routing protocol..... Well, it used to be. In 2013 Cisco made EIGRP an open standard, by releasing it as an informational RFC.
However, What is it actually used for ? Well, it's a routing protocol designed to simplify routing in multi-side networks. Key benefits include:
- Fast convergence
- Support for route summarization
- Scalability for large networks.
In this step, we'll configure EIGRP on the three routers and test connectivity.
- Enable EIGRP on All Routers
What we need to do is enable EIGRP and assign an autonomous system number to it, this is used to define the routers that will participate in the same EIGRP process and exchange routing information. I will be using the number 1 as my defined group.
Then we will advertise our directly connected routes.
London HQ router configuration
London-HQ-RT#enable
London-HQ-RT#config t
London-HQ-RT(config) router eigrp 1
London-HQ-RT(config-router) network 192.168.1.0 0.0.0.255
London-HQ-RT(config-router) network 10.0.1.0 0.0.0.3
London-HQ-RT(config-router) network 10.0.2.0 0.0.0.3
London-HQ-RT(config-router) end
London-HQ-RT(config)exit
London-HQ-RT#write memory
In EIGRP and other routing protocols like OSPF, we use wildcard masks, to specify the range of IP addresses. That is why you see 0.0.0.255 and 0.0.0.3. We know this because /24 is 255.255.255.0, so the wild mask would be 0.0.0.255 and the serial connections are a /30 which gives us 255.255.255.252, leaving us with 3 remaining.
We will now carry on with the next router configurations.
Manchester HQ router configuration
Manchester-BR-RT#enable
Manchester-BR-RT#config t
Manchester-BR-RT(config) router eigrp 1
Manchester-BR-RT(config-router) network 192.168.2.0 0.0.0.255
Manchester-BR-RT(config-router) network 10.0.1.0 0.0.0.3
Manchester-BR-RT(config-router) network 10.0.3.0 0.0.0.3
Manchester-BR-RT(config-router) end
Manchester-BR-RT(config)exit
Manchester-BR-RT#write memory
We can see on the configuration above that a new neighbor has been specified with 10.0.1.1
Glasgow HQ router configuration
Glasgow-Data-RT#enable
Glasgow-Data-RT#config t
Glasgow-Data-RT(config) router eigrp 1
Glasgow-Data-RT(config-router) network 192.168.3.0 0.0.0.255
Glasgow-Data-RT(config-router) network 10.0.2.0 0.0.0.3
Glasgow-Data-RT(config-router) network 10.0.3.0 0.0.0.3
Glasgow-Data-RT(config-router) end
Glasgow-Data-RT(config)exit
Glasgow-Data-RT#write memory
- Verify EIGRP Neighbors
We can run the following command on the routers to confirm that EIGRP neighbors have been established.
Glasgow-Data-RT#enable
Glasgow-Data-RT# show ip eigrp neighbors
On the Glasgow device, we can see that we are neighbors with London and Manchester.
- Verify Routing Table
We can use the following command to check the routing table on all routers
Glasgow-Data-RT#enable
Glasgow-Data-RT#show ip route
We can see that the routes in Glasgow are being learned by EIGRP with the "D" indication.
We can now check the other two routers to see if they're doing the same.
- Optimize with Route Summarization
To simplify the routing table, we'll summarize routes on the London HQ router. We use this technique to combine multiple specific routes into one, combined into a single summarized route. This can be done to reduce the size of the routing tables and make the network more efficient and scalable.
London-HQ-RT#enable
London-HQ-RT#config t
London-HQ-RT(config) interface serial 0/1/1
London-HQ-RT(config-interface) ip summary-address eigrp 1 10.0.0.0 255.255.252.0
London-HQ-RT(config-interface) end
London-HQ-RT(config) exit
London-HQ-RT# write memory
Now we can do a "show ip" route on the London router to see the new summarized route.
We can see that the summarized route 10.0.0.0/22 combines the subnets 10.0.1.0/30, 10.0.2.0/30 and 10.0.3.0/30 into a single entry.
We can also see the directly connected routes. The 10.0.1.0/30 and 10.0.2.0/30 are still locally connected and visible on the London HQ router for internal use.
And we can see the routes for Manchester and Glasgow LAN's are correctly learned via EIGRP
- Test PC Connectivity
Now we can try and ping across sites. We can start with London and try and ping the PCs in Manchester and the Server in Glasgow.
Let's use PC1 in London and ping PC4 on 192.168.2.2 and then ping the Backup server in Glasgow on 192.168.3.3
Both PC1 in London can ping PC4 in Manchester and the Backup Server in Glasgow.
This shows us that EIGRP is working as intended. You should try and ping one PC and server to each site to test connection.
Conclusion
In this post, we successfully configured EIGRP to enable seamless dynamic routing between our multi-site network. With EIGRP and summarization in place, our enterprise network is now dynamically connected, robust, and ready for further enhancements.
In the next post, we'll focus on introducing VLANs and Inter-VLAN routing to segment traffic within each site and improve network efficiency.
Hope this guide has been helpful, and Happy Networking!
Follow the next post of the series here:
Dylan Hughes
