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

tomasflyer at tomasflyer at
Tue Jan 31 02:23:47 PST 2006


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:

"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

Try the New Netscape Mail Today!
Virtually Spam-Free | More Storage | Import Your Contact List

More information about the freebsd-questions mailing list