Switch slow in one direction

[OverWorked]

Hello,

 

I have a Netgear FS726TP switch serving one room, linked via a cat6 cable and a 1Gb port to the main cab.

 

Copying files from the server to a client through the switch is really slow (0.5Mbps). Copying files from client to server is much better upto 80Mbps.

 

24 x 100Mb ports to clients in the room

1 x 1Gb port to the main cab

 

I've tested the cat6 cable by plugging a laptop straight into it and get good speed in both directions. This only occurs with traffic through the switch.

 

I've tried using the other Gb port on the switch (it has two) it makes no difference.

 

Logging onto the switch's web interface reveals nothing - it reports that the Gb ports are running at 1000Mbps.

 

Any ideas?

 

Thanks.

[SYNACK]

Have you tried testing using large pings to and from the server to a station:

 

ping server -l 6500

 

Also have you tried disabling or enabling extra gigabit features like jumbo frame support on the local switch.

[OverWorked]

Thanks. I've pinged in both directions and get the same speed in both directions. 12ms for 65000 bit (or is it bytes?) packet size. This makes it more mysterious.

 

The problem occurs when students with large profiles log on in this room, or there's a large software deployment, or I just try to copy large folders with Windows Explorer from the server to the client.

 

It doesn't happen if I plug straight into the Gb cable, so it's definitely related to the switch.

 

I can't find anything configurable for jumbo frames or anything gigabit related.

 

I'm tempted just to replace the switch, rather than spend hours on it.

[john]

Any of the clients ports looped back? Maybe a full powercycle of the switches at both ends for good measure? New firmware for the switch?

[Michael]

So are you saying this happens on all workstations? It could be a firewall or an application scanning incoming traffic.

 

This would make sense as I am sure you don't have any firewalls enabled on the server, but on the client you may do.

 

As a temporary measure, disable all security software (or even better uninstall it completely) and disable any firewalls, then repeat the test.

 

Alternatively (if possible) move a switch from a location that is working to this location. Be interesting to see if you have the same results or not.

[meastaugh1]

Could it possibly be a duplex mismatch? Are both switches at either end Netgear? Both set to Auto-1000 or equivalent?

[Oops_my_bad]

In my experience we've always had trouble with netgear FS* switches. If you can afford them, go for any of the GSM* ones.

 

Are you using VLAN's by any chance?

[OverWorked]

@john - We had a power outage this morning, so that forced a full powercycle. The problem has gone away for now - I can send files in both directions at around 40 - 80 Mbps again.

 

@Michael - It's definitely not the clients. I'm using a laptop to test. It worked fine plugged into any other switch. It just had the problem (as did everything else) plugged into that particular switch.

 

@meastaugh1 - I suspect you're right. I'm working on that theory now. But I'll probably have to see if the problem comes back first.

 

@Oops_my_bad - No we're not using VLANs.

 

The problem's gone away for now, but I suspect it'll be back. Thanks everyone.

[Michael]

A duplex mis-match didn't really come to mind, because it would affect traffic in both directions, but it was happening only in one direction.

[OverWorked]

Spent several hours on it and still never did find the correct solution.

 

The problem occurs even though both switches are reporting 1000Mbps full duplex for the link.

 

In the end I just moved the cable from the 1000Mbps port to a 100Mbps port on another switch in the main cabinet.

 

It's not ideal, but at least the link is a lot faster now at 100Mbps, than it was at 1000Mbps [sic].

 

It's just one of those problems I'll have to fudge, having spent too much time on. It'll probably keep me awake for weeks.

Edited June 4, 2008 by OverWorked
spelling

[maniac]

Has the cat6 cable actually been fully tested at GBs speed remembering 100mbs only uses 2 pairs of the cable, but 1gbs speed uses all 4 pairs so it might be possible that one of the two normally un-used pairs is faulty, which wouldn't show up unless a GBs signal was put through it, hence the reason it works ok at 100mbs.

 

just an idea.

 

Mike.

[OverWorked]

Thanks. I hadn't thought of this. I'd just assumed that because it worked at 100Mbps it was a good cable.

 

That's the next thing to try. I'll get a desktop PC with a gigabit NIC and try that.

[OverWorked]

Just to finish this thread:

 

I've tested both switches and the cable seperately and can't find a fault - they're all good.

 

I've even replaced the cable with another 30m cat6m and the problem's still there.

 

The gigabit switches work well on their own and with other switches, but join them together and traffic in one direction in 0.5Mbps at best.

 

I've connected the cat6 cable to a 100Mbps switch at the main cab and I'm getting 70-80 Mbps. I'll just have to live with that.

 

I've given up on this and decided that the two gigabit switches simply don't *like* each other.