[c-nsp] Network Topology Mapping

[Justin Shore]

Roger Oliver wrote:
> Maybe not the best way but it has worked for me in the past. 
>  
> Enable CDP on all your network devices (Just for a little whlie).
>  
> Now logon to each record the "CDP neighbor detail" output
>  
> Pick a router/switch say "core-1" 
> How many CDP neighbors? 
> Which ports are they connected to? 
> Draw these connections on paper this is just a rough draft so a big box with lines and labels is fine.
>  
> Once you've done that pick one of these neighbors and see what they see and so on. 
>  
> There are I am sure tones of better ways to do this. But when I go somewhere to consult and they don't have clear documentation this is how I get started. 

This is exactly how I do it too.  I also verify everything visually.  On 
my grand flowchart I also label interfaces and then go back to Visio and 
start drawing it.  It's a slow tedious process but that's the only true 
way to determine the complete network topology.  I've often non-CDP 
enabled devices on the network that complicate a CDP discovery. 
Detailing exactly what connects to where visually is the only safe bet.

I've also used LAN Surveyor for a quick sanity check for before and 
after maintenance windows to make sure that we didn't accidentally lose 
a large portion of a network in the process.

I'd recommend a manual check over an automated check any day of the week.

Justin