Introduction

EIGRP has the ability to automatically summarize at classful boundaries. This can cause problems when implementing discontiguous subnets because the summary will prevent EIGRP from routing between the discontiguous subnets.

What is a disadvantage of using eigrp automatic summarization?

One disadvantage of using EIGRP automatic summarization is that it can cause problems with routing if you have different subnets within your network that need to be accessed. This is because summarization will lump all of these subnets together and present them as one summary route, which can then cause problems if certain subnets need to be accessed. Another disadvantage is that it can make your network harder to troubleshoot because you will not be able to see the individual routes within the summarized route.

How can you avoid the disadvantage of using eigrp automatic summarization?

EIGRP automatic summarization can cause problems if your network contains discontiguous subnets. For example, if you have a Class C network address with a subnet mask of 255.255.254.0, this network would be divided into two subnets: 192.168.1.0/23 and 192.168.2.0/23.

If EIGRP is configured for automatic summarization on this network, the router will automatically summarize the routes for these two subnets into a single route: 192.168.0.0/22. This can cause problems because the summary route does not accurately reflect the actual state of the network, and it can prevent some traffic from being routed correctly.

One way to avoid this problem is to manually configure EIGRP to disable automatic summarization on any interfaces that are connected to discontiguous subnets.

Conclusion

There are a few potential disadvantages to using automatic summarization with EIGRP. First, it can lead to suboptimal routing if traffic patterns change and the summary no longer covers all of the needed routes. Second, it can make troubleshooting more difficult since you may not be able to see all of the available routes. Finally, it could potentially cause problems if you have different types of devices on your network that use different subnet masks.