[GRLUG] Slightly OT, .. Troubleshooting a network?

[Adam Tauno Williams]

On Mon, 2010-09-20 at 11:29 -0400, Michael Mol wrote:
> On Mon, Sep 20, 2010 at 11:15 AM, Don wood <donlumber at comcast.net> wrote:
> >  On 9/20/2010 11:13 AM, Adam Tauno Williams wrote:
> >> On Sat, 2010-09-18 at 23:58 -0500, L. V. Lammert wrote:
> >>> Have a problem with a small network (six machines, one server&  router) -
> >>> some of the Windoze machines are taking *minutes* tologin on the server,
> >>> and I suspect that some of the network gear/cabling may be having
> >>> problems.
> >>> Other than pawing through packet dumps or ramdonly running cables to
> >>> byass what's in the walls (already swapped the switch), is there any way
> >>> to collect 'statistics'? Collisions? Packet re-sends? Conversation
> >>> failures?
> >> If you are using a managed switch it knows all [or most] these things.
> >> Otherwise, no.
> > Actually if it's a managed switch you could mirror all port traffic to one
> > port and analyze it with wireshark.
> Yes and no. I think Adam was mentioning problems on IRC a few weeks
> ago where it was unclear whether or not the managed switch was
> mirroring all the packets he wanted, given a VLAN setting.

No, they will mirror all traffic.  Only the drivers [in the Linux
kernel] will discard the vLAN tags when you have the interface in
promiscuous mode.  So in Wireshark you can see all the traffic but you
cannot tell what vLAN it came from.  Which is fine if you have only one
LAN on the switch, otherwise it can be confusing.


-- 
This message has been scanned for viruses and
dangerous content by MailScanner, and is
believed to be clean.