mac in multiple vlan

Unanswered Question

hello

i have mac address in multiple vlan:

10 001a.30da.3c00 DYNAMIC Gi0/2

20 001a.30da.3c00 DYNAMIC Gi0/2

30 001a.30da.3c00 DYNAMIC Gi0/2

40 001a.30da.3c00 DYNAMIC Gi0/2

50 001a.30da.3c00 DYNAMIC Gi0/2

60 001a.30da.3c00 DYNAMIC Gi0/1

70 001a.30da.3c00 DYNAMIC Gi0/2

80 001a.30da.3c00 DYNAMIC Gi0/2


what is the reason of this proble and how to overcome?

10xs

  • 1
  • 2
  • 3
  • 4
  • 5
Overall Rating: 5 (6 ratings)
Loading.
Edison Ortiz Mon, 12/10/2007 - 10:11
User Badges:
  • Super Bronze, 10000 points or more
  • Hall of Fame,

    Founding Member

The mac-address (001a.30da.3c00) could be from a switch and Gi0/2 could be a trunk port.


If so, that's an expected behavior.

mheusing Mon, 12/10/2007 - 10:12
User Badges:
  • Cisco Employee,

Hi,


The mac address belongs to Cisco, so it could be normal and no problem at all, as a switch uses the same MAC address in different VLANs in some environments.

This situation is then not something to overcome, as it likely is the normal behaviour.

Which device is connected to Gi0/2 and Gi0/1? Which protocols do you have enabled, like PVST etc.?


Regards, Martin

Jon Marshall Mon, 12/10/2007 - 10:14
User Badges:
  • Super Blue, 32500 points or more
  • Hall of Fame,

    Founding Member

  • Cisco Designated VIP,

    2017 LAN, WAN

Hi Ali


If gi0/2 is a trunk port this could well be a switch at the other end that you are seeing.


Jon

Edison Ortiz Mon, 12/10/2007 - 10:19
User Badges:
  • Super Bronze, 10000 points or more
  • Hall of Fame,

    Founding Member

Devices connected on that switch may have IPv6 enabled by mistake.


If you go directly onto that switch, you can find the egress switchports on workstation generating that traffic.

Edison Ortiz Mon, 12/10/2007 - 10:27
User Badges:
  • Super Bronze, 10000 points or more
  • Hall of Fame,

    Founding Member

By sniffing the IPv6 packets from a monitoring station and capturing the MAC Address.


Once you have the MAC Address of the workstation, on the switch command line interface, issue:


show mac-address | include xxxx.xxxx.xxxx


Replace xxxx.xxxx.xxxx with the mac-address from the workstation

Edison Ortiz Mon, 12/10/2007 - 11:02
User Badges:
  • Super Bronze, 10000 points or more
  • Hall of Fame,

    Founding Member

The only way to know is to proactively sniff packets in your network.


There are many tools in the market that perform this task, NetFlow comes to mind.

Edison Ortiz Mon, 12/10/2007 - 11:12
User Badges:
  • Super Bronze, 10000 points or more
  • Hall of Fame,

    Founding Member

I don't see any problems with enabling IPv6. You wanted to find out what workstations had IPv6 enabled and I explained how to do it.


Workstations can run IPv6 in your network without causing any problems in general. It's just an additional protocol in the wire.

Actions

This Discussion