This is a post dedicated to people that have just started their CCIE studies. When I first started I wasn’t used to the type of diagrams used in the CCIE workbooks. Even though I have several years of experience and have used VLANs for a long time it was a bit confusing at first. Here are some advice for you to get started.
We need to find out how the devices are connected. We are also interested in what interfaces that are trunking. I do it like this, I open notepad and type:
sh cdp nei
sh int trunk
There should be an newline at the end. I then paste this into all the devices. This is faster than typing manually. Producing the layer 2 topology should not take more than roughly 5 minutes.
I can now see what devices are connected and what interfaces that are trunks. I draw four squares and type the switch names inside of them. I then draw the lines connecting them and type the interface number on them. I then draw circles for the routers that are connected to the switches. If a router has multiple connections I draw them as two routers instead of multiple lines from the same router.
This diagram is very important if we need to do traffic engineering at layer two. From what I have heard from the lab the diagrams are very good and the L2 diagram might be the only one that you want to draw.
I then look at the logical topology and identify all the VLANs. Some VLANs are local to the switch and some VLANs connect to routers and other switches. I make a list with the routers and their local port and to what port they connect to in the switch and what VLAN that should be used.
Then I use notepad again and from my list I look at what interfaces should be assigned to which VLANs and type
swi mo acc
swi acc vl 146
I do this for all interfaces and for all switches and then paste the config in the switches.
How do I know what VLANs need to be created. Well, the VLANs that have interfaces assigned in the local switch is a no brainer. We definately need them. Then you have to look at the transit path if you have a VLAN that spans several switches. Will this switch be in the transit path? If yes, then add the VLAN. If not, then don’t add it. You could just add all VLANs everywhere but that is overconfiguration and could lead to points missed even though I don’t think it is likely that they would deduct points for this.
I have scanned a picture from my notepad that I use when doing labs. You can see it below.