Re: Linksys LAN -- network fails at a switch
From: Sally Shears (sshears_at_theWorld.com)
Date: 01/31/05
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Date: Mon, 31 Jan 2005 10:50:06 -0500
In article <1107144039.741360.206320@c13g2000cwb.googlegroups.com>, prg
<rdgentry1@cablelynx.com> wrote (...some snips...):
> Could it be that the switches and hosts are coming back up after a
> power outage in such a manner/sequence that the problem converges on
> the suspect location ...
This is exactly what I'm worried about.
> ...and craps the spanning tree -- if you're running
> spanning tree, that is.
If "spanning tree" is running, I don't know it. I have SuSE 8.1 and
9.1, pretty standard setup. Linksys consumer switches (the $50 at Best
Buy type) and a WRT54g. These don't provide the spanning tree protocol,
do they? (Googling, I can see that Linksys WET54GS5 does do spanning
tree.)
> I've had times when MACs began appearing on different sides of a switch
> for no apparent reason. This can bring the switch(es) to their knees.
> Hard to "see" it without sniffing the wire and the problem source can
> be difficult to track down.
No loops in the physical wiring. I'm absolutely sure of this.
But... what if a host (and its MAC address) are moved from one part of
the LAN to another?
I move a laptop (Apple OS X) all the time from wireless (with a NAT'd
non-routable IP) to wired (with fixed IP) at the same OR different part
of the network to outside the building (i.e. yet another IP somewhere
else on the internet). Could moving this Mac's MACs be causing the
problem?
FWIW, the Mac laptop has two nics, one wired and one wireless.
Different MAC addresses. OS X in most configurations automatically
changes from one nic to the other as needed. Recently someone opined in
alt.os.linux.suse "a host with two nics on the same LAN is trouble." I
wonder if I should start being extremely careful that no laptop ever
has ethernet plugged in which it's wireless card is operating. Anyone
have comments on two-nics-same-LAN?
I've seen the problem three times
- Twice with the moving laptop outside the building
- Once after a power failure with the laptop in it's usual place on
the LAN.
> Resetting the switches clears the tables and you start clean again.
> After some interval X, the problem accumulates/reappears and brings the
> switches down again.
Yup, that sounds like what I've seen.
> Double check, then double check again, that there are no loops in the
> physical pathways.
No loops in physical wiring. Is it conceivable that I created a loop
involving wireless via the Apple OS X auto-network-config when I
plugged into ethernet with wireless still running? I'll watch out for
that.
> Tried swapping out the "bad" switch with one upstream/downstream or
> sibbling to see if you can make the problem "follow" the switch.
A little hard to tell, but I do have one suspect switch which I'll
watch.
> good luck -- you likely need it ;)
> prg
> email above disabled
PRG, I really appreciate the suggestions and investigation protocol.
Thank you.
-- Sally
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