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