How many IP address aliases can practically be used on one physical Ethernet interface?

Hi,

I am implementing and using a test bed simulating a huge amount of IP clients, each preferable having a unique IP address. There is no, no way to have an individual physical interface for each simulated client so I use IP aliases. Currently it runs on Linux and there is a limit of 256 IP addresses per interface, among other things due to a hard array limit in Linux net-tools ifconfig. There also seems to be other limitations like linear searches in net-tools as well as in kernel networking code. Just changing the array limit changed the problem to being one of stability and performance.

So I became quite optimistic reading about Virtual Hosts and IP aliases in the FreeBSD handbook chapter 11.9:

http://www.freebsd.org/doc/en_US.ISO8859-1/books/handbook/configtuning-vi
rtual-hosts.html

"A given network interface has one "real" address, and may have any number of "alias" addresses".

So is this really true and where is the catch? Will a FreeBSD 6.0 accept for example 8190 IP address aliases each on say five physical Ethernet interfaces? Will IP addresses be manageable to add, list and delete? And how much will networking performance degrade compared to using just a few aliases?

I can add that there is no forwarding or routing through a simulator box except IP traffic to and from the client simulation running inside.

I am maybe willing to change to BSD if there is a chance of success, most Guru UNIX sysadmins running real production say mostly good things about the BSDs. I just need some encouragement... ;-)

Best Regards

Flyer
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