Slow Network

Bluefrog

Have a Windows 2000 server based domain with all XP professional clients (8) and all was working fine until recently with all clients and the server connected via a 16 port hub. We were running Kerio Winroute connected to a Zytel USB modem on the server to share our 4MB broadband connection and all clients had no problems connecting at around that speed.

Then recently we upgraded to the Eircom 12mb offering. They provided a Netopia modem/router as they told us that our Zytel would not support the new speeds.

So I changed the network topography to accommodate the new router/modem basically connecting the modem/router into the hub via the uplink and resetting all machines to use the IP of the router as the default gateway.

This sort of worked in that all machines still have access to each other though at what seems drastically reduced speeds but when I do a broadband speed test from any of the machines connected to the hub I am getting speeds in the region of 650-700 kbs!

Thinking that maybe I didn't need to connect the hub and the router/modem via the uplink port on the hub I tried another port but still the same result.

Along with the slow speeds we are now seeing symptoms of a known issue with our Exchange setup where UDP packets from our Exchange server are being blocked so that clients do not recieve new mail notifications unless they change folders thereby polling the Exchange server and messages linger in the outbox until once again the selected folder on the client is changed.

If I connect the server directly to the router/modem I get the expected normal results in the internet speed tests - about 6500kbs. I'm wondering if since the speed increase is a factor of 10 if that's a clue. All network cards are 10/100.

Anyone got any ideas on what might be causing our drastically reduced internal network speeds - Eircom don't want to know as they say it is an internal network issue but I can't help thinking that the modem/router is somehow involved.

ttm

You missed out the bit about where the clients are getting there DNS server lookups?

Bluefrog

Ah yes, yes I did - they're consulting the server which has a dns server running and this forwards to the Eircom nameservers for external lookups. The server basically consults itself if you know what I mean.

Running nslookups from the clients and server seem to work fine both for internal and external lookups.

ttm

So why not put another network card in the sever and let it do the routing as well. Probably how it was working with the USB modem unless you were using ICS?

Bluefrog

Just tried that today. In that configuration the server gets the full internet speed but the client computers are still limited to about a 10th of it. It made no difference to network throughput or the weird UDP problem although thinking about it, that could have been there since SP2 went on the machines and nobody noticed until now.

Also in that configuration I have the issue of double natting to contend with though I guess I can work around that eventually. Not sure how though and can't see why linking the modem/router to the hub directly should be a problem.

FusionNet

Can I ask you. Are you using a hub, a switch or a managed switch?

Also what kind of cable set up have you, is it a cat5e network and is it installed properly? You may be experiencing a bottle neck effect with the new router?

ttm

Firsty you are using Windows 2000 server and possibly SBS and this is one of those rare occasions where the best bug fix is the next version ie Windows 2003 SBS. If its still availabe W2k3 SBS should only be about 1k for the Server OS and 10 Cals (W2k8 SBS will be along soon). I've set up and used all the SBS versions since they first came out and hated them untill W2k3 which I can recommend as the first MS SBS product that really does what it says on the tin - well mostly

Double NAT isn't really a problem and from what you are saying it looks like the first fix for around 100 euro has to be a new 10/100 switch, if you are still using a hub which is almost impossible to buy now (except via fleabay) it must be getting on a bit. Even with just 8 users you'll see a big difference with a switch. Its even very possible you have one bad network card or port on the hub which is bradcasting crap and slowing the whole network down. Have you checked network speed just by doing a timed file transfer, when busy and when no one else is using the network?

Ideally check your network with something like the Linux Etherape or Etherman apps they both do much the same but can show you graphically were your network traffic is going and the bottle necks - on an old system with a hub they both work great.

Cabling shouldn't be an issue with just 8 computers and a server but worth disconnecting all the clients and just connecting one and testing, might show up an issue in the hub or cabling. I've seen old crushed cable screwup a network (slow as I guess every packet of data had to be retransmitted many times before it was acknowledged) in the same way very long runs will - on a hub this would cause far more of a problem than a switch.

Also check on the server and clients that you don't have protocols running that you don't need, NetBEUI hasn't been used in a while but your network sounds like its evolved over the years and it might have been installed to help old Win 95 clients so uninstall it if its been added.

My guess is you have some broadcast traffic somewhere or everywhere that is just messing up your network.

btw I've also had the same issue once when I was stupid enough to put in an incorrect subnetmask everything worked because the router was spotting my mistake and routing the data between the two networks (in that case server on one and clients on another) but it slowed everything to a crawl. So I'd go back and check evey PC, server, hub, router and cable you have and assume nothing with 8 PC's thats hardly a big job.

ttm

Double NAT was a clue ;););)

Try http://support.microsoft.com/kb/304849 might solve the issue.

Bluefrog

ttm wrote: »

Double NAT was a clue ;););)

Try http://support.microsoft.com/kb/304849 might solve the issue.

The Exchange server sits on the same subnet as the clients so the interface it communicates with them isn't being 'natted'.

FusionNet, it is a hub and yes I understand that a switch would be faster and that's something I intend to address but in this case the speed decrease seems to have happened suddenly and so I'm looking for the reason why. Cabling is CAT5 and it wouldn't be far up my list of suspicions but if nothing else comes to light I will look into it.

TTM, have seen the KB articles on the UDP issue and as I said it may be that this has just been noticed now and always been there since we installed SP2. Will be a few days before I get to implement the fixes to the clients to see if that solves it but hopefully.

It's actually just barebones Windows 2000 server without the SBS bells and whistles - just Exchange 2000 so ISA doesn't come into the picture but Windows Firewall is definitely on the list of suspects for the UDP issues.

The Etherape and Etherman tools sound interesting and I will look into them. Something similar that would run on Windows would be handy in this situation.

Thanks to all for the suggestions - given me some food for thought.

axer

Bluefrog wrote: »

FusionNet, it is a hub and yes I understand that a switch would be faster and that's something I intend to address but in this case the speed decrease seems to have happened suddenly and so I'm looking for the reason why.

:eek: Someone is still using a hub? The first thing you should do is drop the hub. Any increase of traffic will dramatically effect your network performance since all are competing for the same bandwidth and there could be collisions all sides. A bad network card, for example, could be causing crazy traffic which the hub is repeating out all ports causing collisions all sides.

Then if the problem still exists remove some clients from the network and check.

ttm

Bluefrog wrote: »

It's actually just barebones Windows 2000 server without the SBS bells and whistles - just Exchange 2000......

wow how can you justify buying Exchange and Windows server as separate packages just for 8 users - and still be using a hub?

btw I really have seen loads of dead and dying hubs and switches that cause eveything from slow network speeds to annoying hard to pin down intermittant issues.

Did you try obvious test yet? Server and 3 clients plugged into the netopia? Would show if the problem was in the hub.

Bluefrog

ttm wrote: »

wow how can you justify buying Exchange and Windows server as separate packages just for 8 users - and still be using a hub?

btw I really have seen loads of dead and dying hubs and switches that cause eveything from slow network speeds to annoying hard to pin down intermittant issues.

Did you try obvious test yet? Server and 3 clients plugged into the netopia? Would show if the problem was in the hub.

Well, this is a network I inherited rather than built so I can't speak to the ins and outs of how it came to be this way nor 'justify it' . I think the next iteration could be to open source the whole thing - seems like we are sacrificing hardware and software updates here for licensing fees.

Not on-site full time so will be a while before I get to go through all this but I think the best solution for now is to turn on connected pcs one by one and look at network speed - flakey network card or flakey hub will become apparent then.

Found an own brand switch on dabs.ie that is cheap as chips so will arrange to get that.

axer

Bluefrog wrote: »

Found an own brand switch on dabs.ie that is cheap as chips so will arrange to get that.

Why not purchase a decent switch for the sake of a few extra euro - it will save you in the longterm. Im not talking about a cisco 2950 series but even a linksys or something.

ttm

Bluefrog wrote: »

Well, this is a network I inherited rather than built so I can't speak to the ins and outs of how it came to be this way nor 'justify it' . I think the next iteration could be to open source the whole thing - seems like we are sacrificing hardware and software updates here for licensing fees.

Not on-site full time so will be a while before I get to go through all this but I think the best solution for now is to turn on connected pcs one by one and look at network speed - flakey network card or flakey hub will become apparent then.

Found an own brand switch on dabs.ie that is cheap as chips so will arrange to get that.

No need to even use the hub for a test, as I said try the netopia's 4 port switch with 3 PC's and the server if the works there's a good chance that a cheap 8 port switch will fix the problem. Obviously the server and one PC will need to use the switch on the netopia router unless you splash out on a 12port switch :eek:

You my find SBS has everything you need for 8 users, I've installed at least a couple of dozen copies (I mean originals ) and for 10 users at less than 1000 euros for the Std version with Exchange its hard to justify anything else unless you are an open source guru and know the stuff so well that your admin costs don't make the open source more expensive than MS's offerings. Hopefully MS won't screw up SBS 2008 but it looks like they might be going that way on pricing - shame as it was hard not to sell sbs 2003 on price.

I know a lot of IT companies don't like selling and installing SBS versions as it doesn't make as much money for them.

btw dabs is not my favourite company, just techie predudice, I would even prefer to give my money to PCWorld rather than dabs. If your in Dublin and in the "trade" try Wood Communications http://www.woodcomm.ie/ , seem to remember they only do Allied Telesyn switches but I never had any problem with them.

Bluefrog

I do think I'll do the pcs one by one just to check that its not a flakey card in one of the clients seeing as how this was all so sudden. Still in the throws of getting my head around the peculiarities of the setup there.

I'm a web developer, only doing this network admin as a family favour so the less time it takes the better. Have dealt with dabs before without issue and as for their own brand stuff, bought a few things from the at this stage and never had issues. Thanks for the link though - will check it out. Always good to have options.

I run a little Ubuntu based network here at home so I think open sourcing is a feasible alternative in time.

Bluefrog

Just to update on this - I bought the DABS white label switch and that sorted the issue - great piece of kit for the price - does exactly what it says on the tin.