I'm trying to generate a map of the physical network just from the configuration of every item in the network (switch, router). But the only way I found to be sure an Equipment is plug to another is on the interface description. If the description is badly/wrongly/not filled, I can't assert who is plugged.

The only bit i'm sure of, is on what side a MAC address is from an interface (from the Mac address table).

So my question is : Is there a way to know who is on the second end of a link from my switch/router configurations ? (When I say configuration I mean show running config for Cisco etc...)


No. A interface description is just a label. The only way to find out what's REALLY plugged in is to show the MAC addresses as you noted.

For networking equipment, if you turned on LLDP or CDP it would make it easier to determine what networking equipment is connected to each others.

But for hosts you need to use the MAC address table

  • I wont have LLDP/CDP. Or anything more than the running config. But I can't find the Mac Addr from the end-point. The only Mac I find is the Mac of my interface port.
    – pwnsauce
    Apr 18 '17 at 10:04
  • Use the command "show mac address dynamic"
    – Ron Trunk
    Apr 18 '17 at 11:09
  • The mac address table give information about who is on the other side of the network right ? Not the directly adjacentes Neighbors.
    – pwnsauce
    Apr 18 '17 at 11:19
  • The MAC address table will give you the address of a device on the other side of a layer 2 link
    – mellowd
    Apr 18 '17 at 11:26
  • But it can be anywhere after the link. It could be 3 switch later or just at the endpoint of the interface. How do I know if that's the second case?
    – pwnsauce
    Apr 18 '17 at 11:28

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