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Counting devices with CAM table

I was attempting to count the number of devices that were connected to a Cisco 6509/Cisco 4000 switch infrastructure without going through and checking each port. (without Ciscoworks). I was considering using the CAM table from the core Cisco 6509 but was concerned I would get a lot of entries from the Cisco 4006s that were in fact system entries and not end-user devices. So I guess my question is

1) Has anyone done this before and can provide any insights.

2) Can anyone provide a link or something that will help me filter the none cisco devices out of the list.

Thanks in advance.

2 REPLIES

Re: Counting devices with CAM table

We've done something similar where I work. The IEEE maintains a registry for Organizationally Unique Identifiers (OUIs), that is, the first 3 bytes of a 6-byte MAC address. The current list is at:

http://standards.ieee.org/regauth/oui/oui.txt

If you're handy with scripting, or if you have a lot of time on your hands, you can manipulate the CAM table from your 6500 switch in a text or spreadsheet program and remove/flag all entries whose first 3 bytes match one of the Cisco-registered OUIs at the link above. There are well over 150 OUIs in the list (I stopped counting at around 150), so scripting might be your best bet. Once all the MAC addresses that are definitely Cisco devices are filtered out, you should have a good idea how many non-Cisco devices you have in your network. However, if you want to know how many devices are connected directly to your 6500, you can get a good idea by counting the number of ports in the CAM table that only have one MAC address associated with them. Ports that have multiple MAC addresses will be switches or hubs.

Hope this helps. Good luck.

Swack

Re: Counting devices with CAM table

Why don't you use some simple tool like Solarwinds Switch Port Mapper, e.g.?

It works similar way like Ciscoworks and is much cheaper...

Regards,

Milan

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