Alcatel Omnistack 6000 Series

[weeleong87]

Just wanna check with people who use this switch here. When i telnet into the switch, Sometimes there is a mac address in a particular port when i click on address table. However, when i go to Ports, advanced security config, I see another mac address table. However, Sometimes, the mac address at the mac address table is present but the one at the advanced security config has nothing. why is this so?

[Tuttle]

I'm not familiar with that particular switch, but I'd guess the first table shows you what's actually sending frames through that port, and the second is a manually-maintained list of allowed addresses. If the entry is blank then anyone who plugs in has access, but if one or more MAC addresses are specified then only those[1] can use the port.

[1] Keep in mind that MAC addresses are trivial to spoof once someone knows the valid address.

[weeleong87]

Hi, since you said that the 1st table is what is actually sending frames. Then how come i can add mac address to this table also?

[Tuttle]

I honestly can't think of a situation where you'd want to do that.

It's easy enough to work out if I guessed right -- start a machine pinging something, then move it to a different port, and see if the entry in the first table moves with it.

If it's the table I think it is, it just tells the switch which port to send traffic to a particular machine out. So if it knows that ab:cd:ef:01:23:45 is on port 3 and it has a frame to send to that address, it goes out port 3. If it doesn't know a particular destination, it acts like a hub and broadcasts the traffic. The table is populated over time by the switch looking at the source addresses on frames, and entries time out after a while to deal with machines that quietly get moved around.