Trying to find source of collisions

[Bill Moran]

In response to Igor Zinovik <zinovik at kspu.karelia.ru>:

>          Hello, net@ readers.
> 
> I'm relatively new to freebsd networking so i'm asking here, because i
> did not found information in man netstat.  I have a machine that suffers
> from collisions.
> 
> Network interface status:
> Name    Mtu Network       Address              Ipkts Ierrs    Opkts Oerrs  Coll
> ed0    1500 <Link#1>      00:80:48:c6:a1:82 35885806     4 23583716     0 134590 
> ...
> rl0    1500 <Link#2>      00:00:1c:dc:b8:d6 23455543     0 36137069     0     0 
> 
> This is ordinary RELENG_6_1, with ed0 and rl0 acting as gateway.  UTP
> cat5 is connected to both NICs.
> 
> So i have three questions:
> 1. What can cause such big collisions number?  Bad UTP cable?  Bad NIC?
> Misbeheaving switch?

Collisions are caused by a nearly saturated network.  If you're seeing
collisions, you need to either reduce the amount of traffic on that
network segment, or increase the capacity of that segment.

However, switches shouldn't have collisions.  Either your switch isn't
really a switch, or something else is wrong.

> 2. Ierr -- seems that some input errors.  What are these errors and what
> can cause them?

My first guess would be that you've got a duplex/speed mismatch between
NIC and switch.  If it's a managed switch, force the speed duplex on both
the switch and the FreeBSD machine to ensure they match.  If it's not a
managed switch, replace it because it's not working correctly and there's
nothing you can do about it.

> 3. Should i ever bother about this issue?

Yes.  Something is wrong and it will be hurting your network performance.

-- 
Bill Moran
Collaborative Fusion Inc.
http://people.collaborativefusion.com/~wmoran/

wmoran at collaborativefusion.com
Phone: 412-422-3463x4023