[leffo]

Hi all!

I've invested in a small switch to be able to use our broadband on both mine and my girlfriends computer simultaneously. And, indeed, it's working quite well. However, according to the switch there's constantly packet collisions occuring (collision led's are always lit). Why is this? Can someone give me an idea on how to troubleshoot things? As far as I can see it doesn't really affect performance (atleast it's fast enough for me) but it got me interested. Is there any useful application that will run under OS X I can use to monitor things?

Sunshine and blue skies,
Leif.

[Camelot]

There's several options here.

First, on your Mac run:

netstat -sp ip

This will give you the protocol stats for your IP connection. Most of the values should be 0.

That will tell you if your Macs are seeing the problems.

If only one computer shows errors, then there may be a problem with that computer's connection.

Secondly, is the switch a 'managed' switch? i.e. can you log into the switch and collect statistics from the switch?

This tends to be a feature of higher-end switches, not home network switches, but it might be an option, and it would let you compare the results with the Mac to see if there really is a problem.

If there really are collissions on your network,they tend to be caused by mismatched speed/duplex on the line.

Does the switch have the ability to tell you whether it's running at 10 or 100 mbps, and at full or half duplex?

running 'ifconfig en0' or the Apple System Profiler will tell you how your Mac thinks the line is configured.

The Mac and the switch need to agree on speed and duplex in order to avoid problems.

[ghporter]

A hub usually worries about collisions because it's basically a common arena, it sort of connects each port's transmit line to every other port's receive line, so collisions are a major problem. They shouldn't be on a switch because of the active, address-checking and directing nature of a switch. Also, unless your switch has a special indicator with a lable that says "Collision" and it can ONLY mean that, you probably aren't having collisions. It's probably just showing some other condition.

[leffo]

GHPorter, upon closer examination of the switch I indeed see that the led I thought only meant collisions also mean that Full-Duplex is being used Thanks for pointing out that possibility.

And, Camelot, netstat -sp ip also reveals that everything is in working order. Just a very small percentage of packets get lost, but I guess that is normal behaviour.

Sunshine and blue skies,
Leif.

[ghporter]

Just because you're paranoid doesn't mean they aren't out to get you! Caution keeps you from going over a clif, even though most apparent cliffs are just the top of a smooth slope. In other words, "better safe than sorry." Enjoy.