I am working with a network containing several Catalyst 3550 switches
at the core and several unmanaged switches of various manufacture
outlying.

In summary, SWITCH_01 sees it flapping across 5 interfaces; Gi0/2,
Fa0/1, Fa0/4, Fa0/19, and Fa0/23. Fa0/1, 19, and 23 are servers.
Fa0/2 is a crossover cable to SWITCH_02. Gi0/2 is fiber connected to
SWITCH_10-Gi0/2.

SWITCH_02 sees it flapping across two interfaces; Fa0/5 and Fa0/20.
Fa0/5 is the crossover link to SWITCH_01. Fa0/20 is a crossover link
to an unmanaged gigabit switch.

SWITCH_10 sees this mac on two interfaces; Gi0/2 and Gi0/1. Gi0/1 is
connected to SWITCH_M1-Gi0/2. Gi0/2 is the fiber link back to
SWITCH_01.

SWITCH_M1 sees it flapping across two interfaces; Gi0/2 and Fa0/9.
Gi0/2 is the link to SWITCH_10. Fa0/9 is some device with an HP nic.

Only SWITCH_01 and SWITCH_10 are logging MACFLAP errors even though
SWITCH_02 and SWITCH_M1 are clearly seeing it flap:

SWITCH_01>
%SW_MATM-4-MACFLAP_NOTIF: Host 0201.0000.0000 in vlan 1 is flapping
between port Gi0/2 and port Fa0/4
%SW_MATM-4-MACFLAP_NOTIF: Host 0201.0000.0000 in vlan 1 is flapping
between port Fa0/1 and port Fa0/23
%SW_MATM-4-MACFLAP_NOTIF: Host 0201.0000.0000 in vlan 1 is flapping
between port Fa0/19 and port Gi0/2

SWITCH_10>
%SW_MATM-4-MACFLAP_NOTIF: Host 0201.0000.0000 in vlan 1 is flapping
between port Gi0/1 and port Gi0/2


SWITCH_02>sho mac-addr addr 0201.0000.0000
Mac Address Table
-------------------------------------------

Vlan Mac Address Type Ports
---- ----------- -------- -----
1 0201.0000.0000 DYNAMIC Fa0/5
Total Mac Addresses for this criterion: 1

SWITCH_02>sho mac-addr addr 0201.0000.0000
Mac Address Table
-------------------------------------------

Vlan Mac Address Type Ports
---- ----------- -------- -----
1 0201.0000.0000 DYNAMIC Fa0/20
Total Mac Addresses for this criterion: 1

My questions are:

a) What is this mac address 0201.0000.0000?
b) How do I proceed with troubleshooting this problem?

TIA and sorry for the long post.

JM

In article <48453f4a.496653921@news.giganews.com>,
jmoseby_@_elasticfabrics.com wrote:


Google for 0201.0000.0000, or one of the canonical representations,
02-01-00-00-00-00 or 02:01:00:00:00:00, say, and then work out which of
your servers is trying to do load balancing.

Sam

On Tue, 03 Jun 2008 16:01:33 +0100, Sam Wilson <Sam.Wilson@ed.ac.uk>
wrote:

Sam,

Precicely the answer - thanks. I did do a lot of googling prior to
posting this message, and found nothing. After I posted here, I
googled '02:01:00' in an attempt to find out the manufacturer of the
nic. I found the following enlightening page:

http://www.velocityreviews.com/forum...003-issue.html

which said:
In our case, we are not load balancing any servers, but whoever
installed them installed load balancing on all of them (?). I have
simply un-checked load balancing in the network config on each server
the problem is solved.

Thanks again!

Jim