Network lag

[DVOM]

In our office we use two main programs. One is only installed on one machine but can be and is run on the other (client) machine.

The other program is installed on both machines but the data base is shared between machines.

The problem is we changed the configuration of the network, we used to have a Linksys router and 2 hubs to connect all the machines in the building. At that point there was a few seconds lag in opening a work order.

One hub failed so we got a dlink 16 port switch, now the lag is up to 45-50 seconds which is unacceptable.

We've tried a different router and have tested the cables and replaced one that had a pair of wires crossed. That improved file transfer speeds but the lag in these programs remains.

Does anyone have any ideas what might improve this situation?

TIA

[DVOM]

I've determined that the new switch is the problem as I've reinstalled the hubs into the network and everything works well.

Does anyone have any recommendations at to what brand switch to buy?

[jdc2000]

If you have a Linksys router, then a Linksys switch may be the way to go. You know it has been tested to work well with the router. They have some 16 and 24 port models to choose from. If you have any Gigabit ready PC's, you may want to consider a Gigabit capable switch also.

[DVOM]

I exchanged the dlink switch for a 16 port Linksys switch. Out of 9 machines in the building, 7 immediately worked correctly. Two others, mine being one of them, were unable to see the network or the internet.

Oddly I could scan the network with a LAN scan program and see all the other machines that way. I could also ping all the other machines.

I never did resolve the problems with those two machines and finally used a hub to connect those two.

Is this a common type of problem with switches?

[jdc2000]

That is not generally a common problem. What brand(s) of network cards are in the two machines that could not see the network when connected using the Linksys switch? Did you try different ports on the switch? (Ports can go bad on them.) I generally try to stick with one brand for all networking components. That way you know they have been tested to work together. You will sometimes get two components, like a network interface card and a hub or switch, that just don't play well together. You can sometimes get them to work by adjusting the driver settings, but that doesn't always work and is usually a pain to mess with.

[CataclysmCow]

It's likely you are having a link/duplex setting issue. Either some hosts are not autonegotiating correctly or are incorrectly forced into the wrong mode.

I'd check that some machines weren't manually set to 10Mbps/Half-duplex when you had that hub. If a machine is set to half-duplex and connected to a switch with full-duplex hosts you'll run into what you are experiencing (you'll get extreme packet loss and backoffs on the half-duplex link) You can also set those other problem machines to 100Mbps/Full-duplex to troubleshoot autonegotiation issues.

It could also be a cable issue. Different network appliances are more capable of handling signals that are bordering out out of tolerance. Your existing runs may be out of acceptance. If it's feasible you may want to grab one of the problem machines and bring it to the switch and use a patch cable to test it out.

If you swap patch cables do you notice that the problem lies always with the same ports on the switch or is it always the same PCs regardless of switch port?

Does anyone have any recommendations at to what brand switch to buy?

I'm partial to Nortel and Foundry. They are prohibitively expensive for a small office, but you can find older models for cheap (comparitively) on eBay. If you want new/retail I'd look at SMC. IME, they are very dependable for the cheap, SOHO class switches. D-Link's SOHO line is pretty good, but I'd stay away from their home networking switches. Linksys should just be avoided altogether when it comes to switches.

[DVOM]

jdc2000, I tried switching ports used with no success and I've now got a linksys router and linksys switch so I've got that covered. Due to distance one of the problem machines has now been changed to wireless and is working.

CataclysmCow, I had already tried staticly setting the NIC's to 100Mbps/full and half-duplex with no success and had set them back to autodetect. Today a customer who is a network admin also thought it might be an autonegotiation problem and he thought the switch may be defaulting to the slowest possible setting and suggested I try 10Mbps/half-duplex.

That worked. I then tried 10Mbps/full-duplex and that also works. In fact this machine works as well or better than it ever has. I'm tempted to leave it as it is. Does this host running 10Mbps affect the entire LAN? In other words does the entire LAN run at the speed of the slowest part?

[jdc2000]

If you have the machine that is set at 10mbps connected to an autosensing port, the slower speed should be in effect only for that machine. It should not slow down the whole network.