On Thu, Feb 7, 2013 at 2:45 PM, <m.roth at 5-cent.us> wrote: >>> >>> Let's try ASCII art: >>> (campus net)->[vlan]->[new switch in rm. 1]-> server 1 >>> \ -> server 3 >>> \->[switch in rm. 2]->server 2 >>> >>> And he was seeing traffic between 1 and 2 on 3. And he tried another >>> server in rm. 1, and saw it. >>> >>> Does that make it clearer? >> >> Do you have a huge number of machines on this network? The switches >> have to store the whole table of all MACs on each side for the ports >> and a 3750 should default to default to somewhere between 3K and 12K >> depending on the configuration. A 'show mac address-table count' on >> the switch should show the number of active entries and the available >> space. I've never had to fiddle with that, but there should be >> commands to tune the size and aging times. > > No, not huge numbers. The old switch they replaced was a 48 port, of which > *maybe* 2-3 were empty. The new -they've got two of them cabled together > (and there is much rejoicing). I don't believe *we* can get on their > managed switch. *sigh* Not just on 'that' switch. It has to learn the MACs of all machines across all interconnected switches across all the VLANs trunked to/through it. They'll age out periodically making the switches broadcast to forgotten/unknown targets but that should get resolved early in the arp process before tcp connections send big packets. -- Les Mikesell lesmikesell at gmail.com