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Author Topic: Duplicate MAC Learn on multiple ports on switch  (Read 3443 times)

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Offline Lalitdantu

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Duplicate MAC Learn on multiple ports on switch
« on: July 02, 2013, 11:08:14 PM »
Hi,

Need your help in identifying the cause of a duplicate MAC being learn on multiple ports on ERS 8600 running version 5.1.0.1. below are the trace logs from the device.

[06/29/13 00:49:45:116] tMainTask VLAN_MGR: vlan_mgid.c: 228 : vlanLearnMacAddrFromIstMsg: addr=00:1b:78:2f:1f:be port=3/8 vid=001
[06/29/13 00:49:54:333] tMainTask VLAN_MGR: vlan_mgid.c: 228 : vlanLearnMacAddrFromIstMsg: addr=00:1b:78:2f:1f:be port=3/8 vid=001
[06/29/13 00:49:59:883] tMainTask VLAN_MGR: vlan_mgid.c: 228 : vlanLearnMacAddrFromIstMsg: addr=00:1b:78:2f:1f:be port=2/7 vid=001
[06/29/13 00:50:00:599] tMainTask VLAN_MGR: vlan_mgid.c: 228 : vlanLearnMacAddrFromIstMsg: addr=00:1b:78:2f:1f:be port=3/8 vid=001
[06/29/13 00:50:10:433] tMainTask VLAN_MGR: vlan_mgid.c: 228 : vlanLearnMacAddrFromIstMsg: addr=00:1b:78:2f:1f:be port=1/3 vid=001
[06/29/13 00:50:10:633] tMainTask VLAN_MGR: vlan_mgid.c: 228 : vlanLearnMacAddrFromIstMsg: addr=00:1b:78:2f:1f:be port=3/1 vid=001
[06/29/13 00:50:14:749] tMainTask VLAN_MGR: vlan_mgid.c: 228 : vlanLearnMacAddrFromIstMsg: addr=00:1b:78:2f:1f:be port=3/8 vid=001
[06/29/13 00:50:30:499] tMainTask VLAN_MGR: vlan_mgid.c: 228 : vlanLearnMacAddrFromIstMsg: addr=00:1b:78:2f:1f:be port=3/3 vid=001
[06/29/13 00:50:30:899] tMainTask VLAN_MGR: vlan_mgid.c: 228 : vlanLearnMacAddrFromIstMsg: addr=00:1b:78:2f:1f:be port=3/8 vid=001
[06/29/13 00:50:39:733] tMainTask VLAN_MGR: vlan_mgid.c: 228 : vlanLearnMacAddrFromIstMsg: addr=00:1b:78:2f:1f:be port=4/3 vid=001
[06/29/13 00:51:00:516] tMainTask VLAN_MGR: vlan_mgid.c: 228 : vlanLearnMacAddrFromIstMsg: addr=00:1b:78:2f:1f:be port=1/3 vid=001
[06/29/13 00:51:23:0] tMainTask VLAN_MGR: vlan_mgid.c: 228 : vlanLearnMacAddrFromIstMsg: addr=00:1b:78:2f:1f:be port=3/8 vid=001
[06/29/13 00:51:23:133] tMainTask VLAN_MGR: vlan_mgid.c: 228 : vlanLearnMacAddrFromIstMsg: addr=00:1b:78:2f:1f:be port=4/8 vid=001
[06/29/13 00:51:25:83] tMainTask VLAN_MGR: vlan_mgid.c: 228 : vlanLearnMacAddrFromIstMsg: addr=00:1b:78:2f:1f:be port=3/8 vid=001
[06/29/13 00:52:04:933] tMainTask VLAN_MGR: vlan_mgid.c: 228 : vlanLearnMacAddrFromIstMsg: addr=00:1b:78:2f:1f:be port=3/8 vid=001
[06/29/13 00:52:08:133] tMainTask VLAN_MGR: vlan_mgid.c: 228 : vlanLearnMacAddrFromIstMsg: addr=00:1b:78:2f:1f:be port=3/8 vid=001
[06/29/13 00:52:11:33] tMainTask VLAN_MGR: vlan_mgid.c: 228 : vlanLearnMacAddrFromIstMsg: addr=00:1b:78:2f:1f:be port=1/4 vid=001
[06/29/13 00:52:11:166] tMainTask VLAN_MGR: vlan_mgid.c: 228 : vlanLearnMacAddrFromIstMsg: addr=00:1b:78:2f:1f:be port=3/8 vid=001


Last week we saw high CPU spikes in one of the 8600's connected in a chassis cluster and we had opened an ER case for the same has been identified by the ER team. The CPU spikes haven't come up again though but need to identify Root cause so as to avoid the same in future.

By the way this MAC belongs to a HP device, most probably a server which we are trying to figure out.

Please suggest. Thanks in advance.


Regards,
Lalit


Offline Johan Witters

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Re: Duplicate MAC Learn on multiple ports on switch
« Reply #1 on: July 03, 2013, 03:52:38 AM »
There are a few scenario's in which this could happen:

1) loop in the network, but you would notice this fairly quickly if this happens
2) MLT having an issue: an MLT should normally only allow traffic for a certain mac to flow over 1 link. In case something goes wrong with the MLT, it would be possible to get traffic over multiple links..

Either way something is wrong: I would chech the devices connected to the ports mentioned in the log and see if nothing is happening there..
Kind regards,

Johan Witters

Network Engineer
BKM NV

Offline Telair

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Re: Duplicate MAC Learn on multiple ports on switch
« Reply #2 on: July 03, 2013, 11:31:20 AM »
We had a number of problems with duplicate MAC addresses coming from Sun Solaris boxes in our environment in years past.  They had multiple interfaces and would all talk with the same MAC address by default.  That caused a fair bit of CPU spiking on our 8600's until we drilled in to the UNIX guys they could not leave interfaces in default configure and connected to the network.

Offline Lalitdantu

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Re: Duplicate MAC Learn on multiple ports on switch
« Reply #3 on: July 04, 2013, 07:01:55 AM »
Hi Telair,

Can you pls. suggest on what changes were done on the UNIX machines in order to control the CPU Spikes in the network.

Regards,
Lalit Kameshwar

Offline Telair

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Re: Duplicate MAC Learn on multiple ports on switch
« Reply #4 on: July 04, 2013, 09:24:29 AM »
You had to run a specific command that would tell the system to use the NIC MAC addresses instead of the default system-wide one.  Having the same MAC show up on multiple VLAN's and interfaces on the 8600 caused our 8600's CPU to run a lot higher than normal as the ASIC's couldn't figure it out so dumped the traffic off to the CPU to deal with.

Here is the article on what to do with Solaris systems to get them to be nice and stop using a single MAC:

http://www.sunsolarisadmin.com/networking/multiple-interfaces-nics-use-single-mac-address-in-solaris-on-sparc/