On Thu, Feb 7, 2013 at 2:45 PM, m.roth@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.