Date: Tue, 31 Jan 2006 16:38:02 +0100 From: Fabian Keil <freebsd-listen@fabiankeil.de> To: tomasflyer@netscape.net Cc: freebsd-questions@freebsd.org Subject: Re: How many IP address aliases can practically be used on one physical Ethernet interface? Message-ID: <20060131163802.19300e98@localhost> In-Reply-To: <8C7F4678970ACD2-1EFC-9D50@mblkn-m01.sysops.aol.com> References: <8C7F4678970ACD2-1EFC-9D50@mblkn-m01.sysops.aol.com>
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--Sig_RDzFuy_6FWBNb+D0A808cRa Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: quoted-printable tomasflyer@netscape.net wrote: =20 > I am implementing and using a test bed simulating a huge amount of IP=20 > clients, each preferable having a unique IP address. There is no, no=20 > 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. >=20 > So I became quite optimistic reading about Virtual Hosts and IP > aliases in the FreeBSD handbook chapter 11.9: >=20 > http://www.freebsd.org/doc/en_US.ISO8859-1/books/handbook/configtuning-vi > rtual-hosts.html >=20 > "A given network interface has one "real" address, and may have any=20 > number of "alias" addresses". >=20 > So is this really true and where is the catch? Will a FreeBSD 6.0=20 > accept for example 8190 IP address aliases each on say five physical=20 > Ethernet interfaces? Will IP addresses be manageable to add, list and=20 > delete? And how much will networking performance degrade compared to=20 > 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 --=20 http://www.fabiankeil.de/ --Sig_RDzFuy_6FWBNb+D0A808cRa Content-Type: application/pgp-signature; name=signature.asc Content-Disposition: attachment; filename=signature.asc -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.2 (FreeBSD) iD8DBQFD34RmjV8GA4rMKUQRAiPjAKDpi3zHrHw1nBYYo2m3T9uSOFoGvwCfZu4Q b+BXu+aVaweJUxVKBW/JG4A= =Z02p -----END PGP SIGNATURE----- --Sig_RDzFuy_6FWBNb+D0A808cRa--
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