Layer 2 troubelshooting tools

net_nomad

I work on a large layer-2 network.

when it comes to troubleshooting the only tools that I am aware of is cisco's CDP protocol and that one is vendor specific. sometimes ARP/Mac table help

compared with range of ICMP protocols/tools available for layer-3 ping,traceroute, dns tools, dhcp/bootp

what general layer 2 troubleshooting tools do you recommend or have found useful ?

chmorin

That depends on what you are trying to accomplish. All I have ever found myself doing is running show arp commands, mac address commands (or CAM table commands), or interface commands (sh ip int brief).

Truth be told, I have not found an affective way or remotely or logically map devices that have not been physically mapped out or labeled properly when they are first installed if they are not cisco devices.

You can run show mac add commands on certain interfaces to the their MAC information if needed, and a couple other ways you can use show commands to help navigate on the L2 level.

net_nomad

one that is very helpful is plugging the the first part of MAC address into a website will give you the manufacturer of the device.

I do this because I have a user who keeps plugging in residention wireless routers that that is also confiugred as a DHCP server. so it will show the mac being owned by Linksys, d-link etc, cisco

if there only was away to find out what kind of device e.g computer, switch, router would have been nice.

Met44

net_nomad wrote: »

what general layer 2 troubleshooting tools do you recommend or have found useful ?

Linkloop or similar for Unix/Linux systems.

vinbuck

Show mac address-table and show arp used with regular expressions like | incl can be very powerful. You can usually track a rogue node down to the port on a large network by using a combination of MAC Address and VLAN info.

EliZ_

Here is a link to a small application that I've been making that might be usefull to map the network.

The goal is to create a map of a network, with Switches, clients(name resolved)
Current Problems:
Still only SNMPv1 support.
Devices can not be removed.

Still very limited, but since I'm done with my CCNP, hopefully I will have more time over to complete a non Beta version soon.

networking-forum.com - View topic - Network Mapping

Feel free to post a request in that link if you think something vital is missing.