[AusNOG] The occurrence of duplicate MAC addresses

[Tom Berryman]

Actually bad luck to both guy #1 and #2 really- though you would *presume I wouldn't be larger vendors "recycling" their MAC allocation, but the smaller vendor less likely to have their hardware located at a large peering point...
I have suspected -for 12 months or so- iPads to do this presenting issues on large scale L2 deployments when the units were purchased in bulk, i.e. a secondary school purchasing 600 or so in 1 order and connecting to a campus wide L2 domain.... Anyone else out there experience this with iPads?
--Tom

-----Original Message-----
From: ausnog-bounces at lists.ausnog.net [mailto:ausnog-bounces at lists.ausnog.net] On Behalf Of Gavin Tweedie
Sent: Friday, 8 February 2013 6:07 PM
To: ausnog at lists.ausnog.net
Subject: Re: [AusNOG] The occurrence of duplicate MAC addresses

On 8/02/2013 2:51 AM, Paul Brooks wrote:
> ...remembering that duplicate MAC addresses aren't actually a problem 
> unless you get two of them on the same broadcast-domain LAN. Within  
> an 'IP Core' there usually aren't many high-node-count broadcast domains.
> Many many point-to-point real or virtual links with 2 addresses, many 
> VLANs with less than 20 nodes perhaps.

Not a lot of large broadcast domains within a SP routed network, but they do occur at the edge of SP networks at exchange points, and in
layer2 backhaul (ethernet DSLAM backhaul, NBN..).

Bad luck for guy #2 who rocks up to the peering point with the same MAC as an existing member eh? Or potentially bad luck for both if nobody notices before they connect.

An interesting stat to know would be what sort of vendor equipment this is occurring on, is it just low end home gateway devices or does the vendor have the same issue on higher end gear?

Gav

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