Layer 3 Switching Overview

In order to understand about Troubleshooting the Layer 3 switching which would be using the switch router, it would be better to have an overview of the same. It would show how a switch router would fit into the network, the architecture of the switch router, as well as the course of a Layer 2 and Layer 3 packet through the switch router. Also, it would include a list of Layer 3 switching software features with brief descriptions of selected features. Before we discuss the troubleshooting the Layer 3 Connectivity of CCIE Data Center, you would be needed to know that you are needed to have a hands-on practice to acquire the skills of Troubleshooting much faster and easier. You could join the courses and mock lab sessions which would be provided by well-reputed organizations like the SPOTO.

A Layer 3 switch router would be performing the following three main functions:

•    Packet switching
•    Route processing
•    Intelligent network services

Layer 3 Forwarding:

By using CEF, each of the line cards is going to maintain a FIB (Forwarding Information Base) table which would be downloaded from the switch processor. Any changes that would be made to the route processor routing table, caused by additions or deletions of routes or route flaps, are going to be updated in the central FIB, which in turn would be updating the line card FIBs. This means that, at all times, all line cards would have a correct map of the network topology.

Troubleshooting Layer 3 Connectivity:

Once you have Layers 1 & 2 workings, your show interface command would show the line is “UP & UP”, it is now time to move on to layer 3, which would be the OSI Network layer. The easiest thing to do here would be to see if layer 3 is working is to ping to the remote side of the LAN or WAN link from this router. Make sure you ping as close as possible to the router to which you are trying to communicate from one side across to the other side.

The following would be recommended taking this interface configuration and comparing it, side by side, with the remote WAN connection so as to ensure that they are the same. You need to ask yourself questions like:

•    Are these interfaces present on the same IP network?
•    Would these interfaces have the same subnet mask?
•    Are there any access-lists (ACL) which would be blocking your traffic?
•    Would you be able to remove all optional IP features to make sure that the basic configuration works before adding additional features that could be causing trouble?

Let’s suppose that now you are able to ping across the link, from one side to another. While that would be considered as a great sign, it doesn’t always mean that everything would be considered as “fixed”. You might still not be able to communicate from a client on the LAN of one router, to a client present on the LAN of another router, due to reasons like improper configuration of IP routing protocols.

It doesn’t end here, there are lots more thing which the candidates are needed to learn for the Troubleshooting the Layer 3 Connectivity of the CCIE Data Center Module. Consider it just a pinch of everything which would have to learn while appearing for the CCIE DC Certification. But worry not! To gain more hands-on training and practice sessions as well as help related to the written exam, acquire the courses which are offered by a well reliable training institute like, the SPOTO.