On Wed, 5 Oct 2005, Andrew Boyce-Lewis wrote:
I am running a bridging network and have discovered that the OSX tun/
tap driver apparently hard codes the MAC address of the tap interface
(so all OSX clients have the same address). ( Tiger version http://
www-user.rhrk.uni-kl.de/~nissler/tuntap/ )
Has anyone else run into this problem? or can anyone suggest any
possible workarounds? I've read that the windows and linux tap
drivers use an algorithm to generate a non-sense MAC address and
assign that to the interface... I suppose that might need to be
implemented for the OSX version.
Here are my comments in the TAP-Win32 source code about this.
/*
* Generate a MAC using the GUID in the adapter name.
*
* The mac is constructed as 00:FF:xx:xx:xx:xx where
* the Xs are taken from the first 32 bits of the GUID in the
* adapter name. This is similar to the Linux 2.4 tap MAC
* generator, except linux uses 32 random bits for the Xs.
*
* In general, this solution is reasonable for most
* applications except for very large bridged TAP networks,
* where the probability of address collisions becomes more
* than infintesimal.
*
* Using the well-known "birthday paradox", on a 1000 node
* network the probability of collision would be
* 0.000116292153. On a 10,000 node network, the probability
* of collision would be 0.01157288998621678766.
*/
James
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