First, collisions are no big deal. They are to be expected when running
half duplex. However, you may not be intending to run half duplex from
the sounds of it. Try hard setting the router and switch ports for both
speed and duplex. It's possible that something caused router1 to
renegotiate, or perhaps the switches renegotiated and both of them
picked the wrong settings. It's difficult to say, but I do know that
it's best not to leave that sort of thing to chance.
Autonegotiation = "A Bad Thing"
There may be other causes but that would be the very first thing I
would check.
HTH,
John
>>> "Jim McDowell" <[EMAIL PROTECTED]> 3/27/01 12:00:20 PM
>>>
Hi,
I have a 3640 ("router1") with IOS v11.2 which is routing between IP
subnets
(class "c" with a one bit subnet mask - using "IP subnet-zero"). There
are
two Ethernet ports on the router, each is connected to a separate
Catalyst
3500 XL switch. The two switch ports are hard set to 10 MBS, duplex
autonegotiate, spanning-tree on, portfast on. I am seeing collisions
and
crc errors on the switch ports that are connected to "router1". The
remainder of the switch ports ( with the exception of a few ports which
I'll
explain shortly ) are connected to 100 MBS fastethernet desktops and
don't
show any collisions...I understand why.
I also have another 3640 ("router2") connected to the same switches, in
the
same manner...for redundancy, I'm told. There are a couple of other
3500 XL
switches cascaded from these...to accommodate the number users. The
LAN
size is about 125 nodes with about equal number of nodes connected to
each
subnet. I'm new here...I have recommended getting rid of the
subnetting
scheme in favor of a classful LAN. Anyway, the switch ports that are
connected to "router2" don't show any collisions/crc errors.
This all started 2 weeks ago. The network has been designed this way
for
about a year.
In short, I can't determine whether routing loops are causing the
collisions
(and if so, why only on "router1"), or whether there's a port
configuration
mismatch between "router1"s Ethernet ports and the switch. Or, maybe
some
piece of hardware has just failed? Any suggestions are welcome.
Jim McDowell
Cisco Certified Network Professional
Network Administrator
Copley Information Systems
858.729.8028
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