SONET and MAC address

Wed Dec 8 21:57:05 UTC 2010

Don't know the FlashWave gear well, but in the Cisco ONS/Cerent world GigE
ports can be configured in different modes, some of which do in fact learn
MAC addresses.  Others emulate a single layer-2 link and as the vendor
stated, would not look at the MAC address at all.

	-Scott

-----Original Message-----
From: Jay Nakamura [mailto:zeusdadog at gmail.com] 
Sent: Wednesday, December 08, 2010 3:33 PM
To: NANOG
Subject: SONET and MAC address

We have a Gigabit Ethernet transport between cities by a vendor.  We found
that when there are identical MAC address that are on different VLANs on
different side of the circuit, one of the VLAN looses packets.  This
situation came up because two different networks that travel over the
Ethernet were using HSRP with the same virtual MAC address.

The vendor says both sides are directly connected to Fujitsu SONET gear and
the equipment doesn't even look at the MAC address so it's not their
circuit.  All I know is, I can't recreate the problem if this circuit is not
in the path.

I haven't worked with Fujitsu SONET gear so I don't know if their claim is
true or not.  I vaguely remember someone talking about some equipment
actually having a builtin switch on the SONET port and that was messing up
the forwarding.

Also, on one side of the circuit, there is a copper to fiber media
converter.  I am going to find out what model this is and see if that could
be the cause.

Anyone have any thoughts on what I should look into or have the vendor look
into?  Anyone run into this situation?

Thanks!