Lessons · Network switches · auditing a switch
Reading a switch you did not configure
Four screens tell you almost everything about a switch you have never seen: the configuration, the VLAN table, the port status and the management address.
Hone is a place to practise programming. This is one of its lessons, written out in full and free to read without an account.
What it is for
You will inherit switches. Being able to describe one in five minutes, from the console, is the difference between owning it and being afraid of it.
How to think about it
Always the same order: what is configured, how it is divided, what is plugged in, and how it is reached. Then compare what you found with what you were told.
Worked example
enableThe # prompt. Every one of these needs it.
show running-configOne. Everything somebody deliberately set, in the order the switch renders it.
show vlan briefTwo. How the box is divided and which ports are where.
show interfaces statusThree. What is actually connected, what is disabled, and which ports are trunks.
show ip interface briefFour. Whether it can be reached at all, and on which VLAN.
show startup-configAnd the one people forget: does what it is running match what it will boot as. On this switch it answers 'startup-config is not present', which is itself a finding: nothing has ever been saved here.
Your turn
Check whether the running configuration was ever saved.
show
Console into a switch
The trap
Auditing from running-config alone. It shows what is set, not what is connected; a beautifully configured VLAN with no ports in it looks identical to a working one.