router metrics

Steven J Lamb redhattedsheep at
Tue Dec 20 14:58:58 UTC 2005

I have been looking at the information you guys gave me and it looks like 
some good tools. although I already have a bandwidth tester called ttcp 
which seems to work great. I guess what I want to know is how process 
intensive iptables gets to be. I am planning on routing aprox 4 class-c 
networks across a 10Mbit/second fiber media converter. I guess the questions 
I have is whether I can get away with using a Linux box or if I should buy a 
used Cisco router. I have essentially a spare server with two Giga bit 
Ethernet ports on it but I don't want to run my fiber through that if it is 
going to slow down my traffic. I don't yet have the equipment or the fiber 
so I can not do an empirical test. if I could then I would be able to do the 
try and tune method. so I guess my question is iptables specific. does any 
one out there know what parts of iptables costs a lot in cpu/memory. my 
spare server is really a dual xeon 2.8 GHz with 3 GB ram dual gigabit 
Ethernet and is currently running a small apache web and my spam assassin 
spam filters. it is by no means being overloaded now but I don't want to buy 
a media converter and find that I don't have the processor power.


Steven Lamb
----- Original Message ----- 
From: "Neil Cherry" <ncherry at>
To: "For users of Fedora Core releases" <fedora-list at>
Sent: Friday, December 16, 2005 6:52 PM
Subject: Re: router metrics

> Chasecreek Systemhouse wrote:
>> On 12/16/05, Steven J Lamb <redhattedsheep at> wrote:
>>> about 10 Mb of traffic through this box and I would like to use
>> Per second?  Per minute?  Per hour?
>> ???
>> A damn small text-only install can route 10MB easily.
> You're going to need to tune the TCP/IP settings. If you have a
> machine that has the 2 Ethernets on 2 different IRQs (I've been
> burnt by machines that only share 1 IRQ (Grrr!)). I know a 1.2G
> machine can do it (mine's tuned to about 6M with lots of processes).
> Here's a link that can give you an idea of what's going on:
> I wish I had the link to the site that helped with tuning, sorry
> I misplaced it.
> BTW, you can get Linux down to an boot size of 1.44M if you use
> something like Floppy Firewall. Move that over to a CF card (don't
> write to it with swap) and it'll run in less than 16M of RAM. The
> CF card will give you the option to put extra utilities on the
> machine. Team that up with Firewall Builder and I think you'll be
> in business.
> -- 
> Linux Home Automation         Neil Cherry       ncherry at
>                         Main site
>                    My HA Blog
>               Backup site
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