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interface descriptions are not used and show lldp/cdp neighbors are completely disabled

F Martinez
Level 1
Level 1

Hello,

 

Let's say interface descriptions are not used and show lldp/cdp neighbors are completely disabled on neighboring devices shown below. And you login to the middle switch, how would you know your neighbors?

 

 

Router<-------->Switch<-------->Switch

Many thanks in advance for your response!

4 Replies 4

Hi,
if you want to know about neighbors, we need to enable CDP or LLDP. that is standard procedure. without that you cannot get, native vlan, IP addresses or device type from neighbor.
but, as a suggestion, you can use ARP table to find the MAC addresses of connected interface and try to use OUI lookup to get network card brand and idea about device type. but that will not give good description about other device.
regards,
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Good luck
KB

Thanks for the response. Can you tell me how I can use OUI lookup?

you can use below link to OUI lookup.
https://www.wireshark.org/tools/oui-lookup.html
Please rate this and mark as solution/answer, if this resolved your issue
Good luck
KB

Using the arp table is an interesting suggestion and is one of the first things that I thought of. But we can not be sure that there will be entries in the arp table for both neighbors. There will be arp entries only is there has been successful layer 3 IP communication from the switch management interface address to each of the neighbors. Of course there is an advantage in looking into the arp table to find the neighbor. If there is an entry then we know not only the mac address of the neighbor but also know the IP address.

 

But an OUI lookup is possible even if there are not arp entries. Looking into the switch mac address table will provide the mac address of each neighbor device.

 

HTH

 

Rick

HTH

Rick
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