North American Network Operators Group

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RE: Peering VLANs and MAC addresses

  • From: Ben Butler
  • Date: Wed Nov 09 05:51:02 2005

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This should sort you out.

 no keepalive
 spanning-tree bpdufilter enable

Kind Regards


-----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf Of
Simon Brilus
Sent: 09 November 2005 10:40
To: [email protected]
Subject: Peering VLANs and MAC addresses

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Hi ,

We are unable to resolve a problem with our peering exchange connection
and would like any assistance.  Our peering setup is a follows:

- Our peering exchange connection goes into switch A
- Switch A has a dark fibre connection to switch B, which is in a
different PoP
- Our peering router is connected to switch B

We use spanning tree across our network to allow the VLANs connectivity
across our network.

The peering exchange has an MoU that only 1 MAC address should be
visible on their switch.  However they see 2 MAC addresses on our port.

- MAC address of Peering router
- MAC address of the port they are connected to on switch A

Is there any way to prevent switch A from presenting the interface MAC
address?  Or is this a symptom of spanning tree that cannot be stopped?

Your input will be most welcome.

The config on switch A is as follows:

interface GigabitEthernet0/5
 description Peering Link
 switchport access vlan 148
 switchport mode access
 speed nonegotiate
 storm-control broadcast level 5.00
 no cdp enable
 spanning-tree portfast
 spanning-tree bpdufilter enable
 spanning-tree guard root


Simon Brilus