[CentOS] OT - odd behavior of Cisco switch

[m.roth at 5-cent.us]

Giles Coochey wrote:
> On 06/02/2013 18:34, m.roth at 5-cent.us wrote:
>> Les Mikesell wrote:
>>> On Wed, Feb 6, 2013 at 11:19 AM, SilverTip257 <silvertip257 at gmail.com>
>>> wrote:
>>>> If one of your hosts intermittently loses connectivity, the switch
>>>> will broadcast that traffic to all ports because it can't find the
host's
>>>> MAC address.
>>>>
>>>> (And what Les said about the switch broadcasting traffic until it
>>>> learns MAC addresses.)
>>> Some spanning tree events will force the switch to re-learn MACs too.
>> I should have mentioned this switch is *only* in use on our subnet,
>> though of course we go through it to go Out There, there are gov't
firewalls
>> outside of it. All the traffic is only on our subnet, in this case, and
>> the weirdness was intermittent.
>>
>> At the time, there were two heavy users (me, doing an offline backup,
>> from one room to another, the latter with the server being hit by me in
it,
>> and at that switch, and another user doing heave scientific computing).
That
>> is, of course, in addition to all the other normal traffic from dozens
>> of other servers.
>>
>> Btw, he's not seeing it today, but I'm not running any more backups just
>> now....
>>
> You may have some trunking issues if you use VLANs, inter-operate these
> switches with non-Cisco equipment and have left every port on the switch
> in the default VLAN1.
>
> Have you actually configured the switch, or did you just plug it in and
> get running?

Unfortunately, *we* don't control these switches. They're from the
networking division, which actually controls networking throughout the
campus. We've had them in, they claim they looked at the switches
remotely, and everything's wonderful.... We'll see what happens next week,
when I do the next offline backups.

Btw, we are on our own VLAN. The switch is on it.

      mark