John - try clearing the ARP table in the router and the switch. (and no, I
don't how to do that on a BaySwitch ;-)
-e-
----- Original Message -----
From: "ElephantChild"
To:
Sent: Tuesday, May 15, 2001 9:42 AM
Subject: Re: Strange connectivity issue [7:4533]
> On Tue, 15 May 2001, John Neiberger wrote:
>
> > Okay, this is driving me crazy!! This just started happening around
> > 2:00 this afternoon and I can't think of a single explanation for it.
> > Here's the deal:
> >
> > PC RouterA RouterB
> > BaySwitch
> >
> > The Bay switch has a management IP address configured with correctly
> > configured mask and default gateway. For some reason, any PC on the
> > subnet that I belong to cannot ping the Bay switch. From any other
> > subnet in our network pings succeed; they only fail from my specific
> > subnet. There are no access lists involved anywhere in this scenario
> > and pings to any other device on the same subnet as the switch will
> > succeed from anywhere.
> >
> > RouterA can ping the Bay switch using a standard ping, but pings fail
> > if I use an extended ping and set the source address to the interface on
> > the same subnet as my PC.
> >
> > I've done traceroutes from a few locations to make sure traffic was
> > flowing correctly and I can see no problems whatsoever. The routing
> > tables of all routers involved look exactly as I would expect them to
> > look. The default gateway and mask is set correctly on the switch. If
> > that were not the case then pings from other subnets would fail as
> > well.
> >
> > I've also telnetted to the switch and from there I can ping anywhere in
> > the network except my subnet. This is baking my noodle and considering
> > I just got back from a vacation in Mexico I'm just not ready for this
> > yet. :-)
>
> It sounds from what you say that the problem subnet isn't the one the
> switch is attached to, but it isn't clear how much the path(s) from the
> switch to it have in common with the paths to subnets that don't exhibit
> the problem. The first thought that comes to mind is that the switch got
> confused and has the wrong MAC address in its ARP table, or the wrong
> port in its switching table, for the first hop to the failing subnet.
> Another possible cause is that at some point, it received an ICMP
> redirect pointing it to a first hop that's no longer present.
>
> --
> "Someone approached me and asked me to teach a javascript course. I was
> about to decline, saying that my complete ignorance of the subject made
> me unsuitable, then I thought again, that maybe it doesn't, as driving
> people away from it is a desirable outcome." --Me
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