On Mon, 3 Oct 2005, Marc Haber wrote:
Gee, I didn't know that. How is the different MAC address set? Naively with ip link set dev eth0.101 address <new-mac>?
Yes.
Does this work with all drivers
Nearly all.
will it give a performance impact (such as requiring the phyiscal interface to run promisc)?
It will most likely make the physical interface run in promiscious mode yes.
Some NIC chips support having MAC filters accepting more than one MAC and on these it is possible the interface does not go into promiscious mode, but most NICs do not have this capability.
But in either case this is rarely a performance impact these days as the traffic is heavily filtered by the network switch anyway and very few frames is seen on the physical network connection with another destination MAC.
While talking on this there is also another very interesting virtual network inteface type available for Linux, namely MAC based VLANs. This allows you to create multiple virtual network interfaces each with their own MAC but sharing the same physical connection. This is not in the standard VLAN driver of Linux but available from the same page as vconfig mentioned before. Combined with the arp_filter functionality this can provide quite interesting solutions to virtual hosting, router redundancy etc.
Regards Henrik
