Cisco – List of directly connected network devices by mac/ip

arpciscomac address

I need a list of all devices that are directly connected to the cisco device I'm connected to through serial. I tried the arp table, but it contains more entries than I want since it spans multiple switches. I have no idea how to know which one is an end user device and which one is another network device.

I'm basically crawling a network and I need to know where to go next.

EDIT:
This is a general cisco-device question. I want to do this from routers, switches and other.

I'm running the commands on a cisco device, looking for any device (not necessarily a cisco device) that is directly connected. And I would also like to know which ones of those devices are other network devices (regardless of brand) and which ones are end users.

Best Answer

You can get some intel on it with the command show mac-address-table vlan <number>. It shows all the dynamically learned MACs and the ports they were learned on. You could then decide, based on your network, if said ports are connected to a switch or end device.

Related Solutions

Cisco – How to find a list of devices connected to the network (IP’s and MACs)

Is a broadcast ping to the subnet from the SVI on the switch (which is low-bandwidth), and using show mac address-table dynamic out of the question?

some-switch#show mac address-table dynamic
          Mac Address Table
-------------------------------------------

Vlan    Mac Address       Type        Ports
----    -----------       --------    -----
   1    000f.257b.ba3b    DYNAMIC     Gi1/0/49
   1    0011.254f.a5be    DYNAMIC     Gi1/0/49
  56    0000.0c57.aa00    DYNAMIC     Gi1/0/49
  56    0004.0ff4.8cf4    DYNAMIC     Gi1/0/49
  56    0004.0af4.c8fb    DYNAMIC     Gi1/0/5

At this point, use your ARP table to map from mac-address to IP address.

Doing this with SNMP is possible, but somewhat painful if you need to know what port each mac-address is on... use dot1dTpFdbAddress to grab the mac-addresses, dot1dBasePortIfIndex to map to interface ifIndex and then ifName to map from ifIndex to a name you'll recognize.

Cisco – Tracking down an invalid source mac address

You could try if the frames can be blocked using a MAC ACL on interfaces and/or on vlans on the access switches. By applying the blocks selectively and checking if the error messages on the 4500 disappear or not, you can home in on the source of the traffic.

Moving cables around to see if the port mentioned in the error message on the 4500 follows could also help, but might prove tricky in a production environment.

Best Answer

Related Solutions

Cisco – How to find a list of devices connected to the network (IP’s and MACs)

Cisco – Tracking down an invalid source mac address

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