Re: How many IP address aliases can practically be used on one physical Ethernet interface?
- From: Fabian Keil <freebsd-listen@xxxxxxxxxxxxx>
- Date: Tue, 31 Jan 2006 16:38:02 +0100
tomasflyer@xxxxxxxxxxxx wrote:
> 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?
After a short test I don't think 8190 aliases will be a problem.
root@africanqueen ~ #ifconfig re0| grep inet | wc -l
18008
root@africanqueen ~ #ifconfig re0 -alias 192.168.10.100
root@africanqueen ~ #ifconfig re0| grep inet | wc -l
18007
root@africanqueen ~ #ifconfig re0 alias 192.168.10.100
root@africanqueen ~ #ifconfig re0| grep inet | wc -l
18008
I don't know if there is a performance degradation on
better hardware, but for my re0 the ftp performance
seems to be the same as with only one IP.
The only "catch" I can see is that it takes a while
to create a few thousand aliases ;-)
On my AMD Athlon(tm) XP 1900+ (1578.59-MHz 686-class CPU)
I get about five aliases per second.
Fabian
--
http://www.fabiankeil.de/
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