Trying to find source of collisions

[Igor Zinovik]

         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?
2. Ierr -- seems that some input errors.  What are these errors and what
can cause them?
3. Should i ever bother about this issue?