Aha! I think you hit the nail on the head with the ICMP redirect. That
makes perfect sense in light of some other configuration changes we made
recently. I'll play around for a bit to see if I can force the router
to send another redirect to correct the issue. Good job! That probably
never would have occurred to me.
John
>>> "ElephantChild" 5/15/01 10:42:07 AM >>>
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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