[134266] in North American Network Operators' Group
Re: The tale of a single MAC
daemon@ATHENA.MIT.EDU (Ian Henderson)
Sun Jan 2 01:01:02 2011
From: Ian Henderson <ianh@ianh.net.au>
In-Reply-To: <C9454E3A.2921F%graham@g-rock.net>
Date: Sun, 2 Jan 2011 17:00:49 +1100
To: nanog@nanog.org
Errors-To: nanog-bounces+nanog.discuss=bloom-picayune.mit.edu@nanog.org
On 02/01/2011, at 2:33 PM, Graham Wooden wrote:
> I encountered an interesting issue today and I found it so bizarre =96 =
so I
> thought I would share it.
Had a fun one with D-Link ADSL modems a few years ago. The MAC address =
used to source PPPoE frames from the ADSL interface was the same in a =
batch of modems. This wasn't a problem when using our wholesaler's ATM =
based DSLAMs, but when we moved users to our own Ethernet based systems, =
we ran into some fun.=20
The DSLAMs were configured to rewrite the user MAC address into a =
constructed address including their DSLAM port and PVC details toward =
the BRAS. Even though this rewrite was occurring correctly, within a =
single DSLAM unit two users with the same real MAC address would have =
five minutes of connectivity each, alternating between the two ports.
Rgds,
- I.=
