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Question about raising a network's ability to handle greater load

F

Fraggable

Platinum Member
Where I work (co-op position, so I'm not in charge here) we have a network with one Win 2003 server, about 150 PCs, 10 WAPs, and 10 networked printers. We periodically have a need to re-image 25 PCs at a time in the computer labs. When we try to image more than one PC at once, our 5 Linksys WRT54GX2 routers go offline and basically shut themselves off and need to be manually reset. Everyone that is logged on is kicked offline and most systems have to be restarted after the network load is removed to be able to get back online. Also, both PCs that were being ghosted encounter errors and fail. To sum it all up, network communication comes to a standstill.

My question is, what needs to be done to increase the network's ability to handle a greater load? Right now 95% of the network is controlled by 5 or 6 24-32 port switches that I believe are 10/100 switches. One of those switches we replaced last week with a 10/100 switch with 2 gigabit uplink ports because of a failure. Do we need to replace the other switches with ones with gigabit uplinks?

The building is wired with CAT5e or CAT6 cable. There is a fiber optic link to the second building.

Thanks for help.
 
you can do a plethora of things, but all depends on how much budget are you working with. Let us know and I am sure plenty of ppl here will throw in some ideas and suggestions.
 
Well it seems pretty clear to me that the limitation is the fact that you are using consumer grade routers in a setting where you should be using large business/enterprise class routers. Cisco comes to mind (of course) but I'm don't know too much in that area so I'll let someone else chime in.

Who knows, maybe they will shoot down my diagnosis. 🙂
 
Trying to figure out why your routers are going offline...

Assuming that you need your Server 2003 connected to the Computer Lab, I'd probably put another (gigabit) NIC in the Server and create a separate subnet for the lab, with its own gigabit switches. Then, anything you do in the Lab won't affect the networking in the rest of the company.

Additionally, it's considered Good Practice to isolate OS Installation Labs from the rest of the network to avoid potential worm infection of newly-installed OSes.
 
We use Netgear and Linksys switches, they are I guess medium-sized business class equipment. We use the Linksys WAPs as convenience more than as a critical part of the network. To clarify, the WRT54GX2's are set up as WAPs, they aren't used as hubs or routers at all. They just create our wireless network and that's all.

Our budget would be something like $5000 over the next couple of years, if it's possible to replace a couple pieces of equipment at a time or as failures occur that would be ideal.

We are an educational institution so there isn't a ton of money floating around.
 
Originally posted by: RebateMonger
Trying to figure out why your routers are going offline...

Assuming that you need your Server 2003 connected to the Computer Lab, I'd probably put another (gigabit) NIC in the Server and create a separate subnet for the lab, with its own gigabit switches. Then, anything you do in the Lab won't affect the networking in the rest of the company.

Additionally, it's considered Good Practice to isolate OS Installation Labs from the rest of the network to avoid potential worm infection of newly-installed OSes.
Click to expand...

Good ideas, I like the idea of putting the labs on their own switch. However, our entire network goes down when this happens, not just the areas that are on the same switches as the lab. Right now I think the lab is connected to 3 of the switches.

EDIT: Oh, I missed where you said to use a separate NIC in the server. We only use one of the 2 NICs in the server now so we may give that a try.
 
Sounds like you need a total redesign.

The only thing that I can thing of hogging the router is a broadcast/multicast storm. Hope you aren't using multicast to image the PCs. The network needs very specific configuration and design to do multicast properly.

For starters...
Have a layer3 core (some kind of layer3 switch at 10/100/1000) with gigabit connections to the other wiring closets. Stay away from stacking switches if you can, that just adds complexity and a possible source of problems when it isn't needed. Use layer3 links to the switches if you can.

Get decent routers

Setup multicast routing and enable it on all switches

Get another switch all by itself to do the imaging, have this on another subnet. So your address design would be:
1 subnet for datacenter
other subnets for the connectio to the wiring closets
subnets for each wiring closet
1 subnet for imaging machines

And if I read correctly you are using multiple links to the switches? Bad idea unless it is setup correctly, and it sounds like it may not be.
 
Good advice Spidey and I understand most of what you're saying, but our network isn't quite as complex as you're thinking. We have one server cabinet with 2 24 or 32 port switches, and one data closet with 4 more 24 or 32 port switches. They all run off of one NIC on the server. The 4 in the closet are daisy-chained together and the one with the gigabit ports doesn't even use those 2 ports. There is a 8-port gigabit switch in the server cabinet, I think it connects to the 2 switches in the cabinet and one line runs to the data closet, the other 4 ports go to a couple of other specialized devices.

We use Symantec Ghost for imaging systems. I do think it uses multicasting to send out the image.

You say to get decent routers - I assume you mean the Linksys wireless routers. They are brand new and serve our purposes very well. We did our research and bought the most powerful wireless routers available at the time of purchase. I'm trying to convince my supervisor that we should get a couple of pre-N routers now.
 
If you're multicasting, then that is indeed your problem. Multicasting is awesome for imaging machines - but only if you're network is setup to support it.s

Your switches are more than likely not setup for multicast - hence every single switch flood the traffic out of every single port. Locking up routers/APs/computers everywhere. Bascially resulting in a net-not-working.

If you don't want to redesign, just get the imaging network onto another IP subnet - this will contain the multicasting to that VLAN only. Put the imaging server on this VLAN. If you can't do that then you'll have to read up on your switches on how to configure multicast on them. You're looking for "IGMP snooping"

oh - and avoid any pre-N stuff like the plague. only standards based gear should be used in a business network.
 
Originally posted by: spidey07
If you're multicasting, then that is indeed your problem. Multicasting is awesome for imaging machines - but only if you're network is setup to support it.s

Your switches are more than likely not setup for multicast - hence every single switch flood the traffic out of every single port. Locking up routers/APs/computers everywhere. Bascially resulting in a net-not-working.

If you don't want to redesign, just get the imaging network onto another IP subnet - this will contain the multicasting to that VLAN only. Put the imaging server on this VLAN. If you can't do that then you'll have to read up on your switches on how to configure multicast on them. You're looking for "IGMP snooping"

oh - and avoid any pre-N stuff like the plague. only standards based gear should be used in a business network.
Click to expand...

I was considering the Linksys pre-N gear, from what I've seen they will be firmware upgradeable to certified-N when it's finally done, but maybe we'll just hold off on that.

We only have 1 server, so I think the best thing for us to do then would be to configure our switches to handle multicasting correctly. Do you know where I can find a guide to doing this? They are primarily Linksys switches but the new one is a Netgear.
 
I am the networking lab tech at my local community college. It is a fairly large campus. I also use Symantec Ghost to multicast removable hard drives at the end of every semester to prepare them for next semester.

I am not working with the IT but from using the network there, I can tell you, that each building is in it's own VLAN - ranging from 10.10.x.x to 10.100.x.x. The Netlab is in its own VLAN (10.80.x.x) which is connected to the 10.70.x.x VLAN of that building. This is done to contain multicast traffic when Ghosting. It works well. They are using two Cisco Catalyst 2950 24-port swtiches trunked together via the two gigabit ports and I believe that one of the gigabit ports connects to a layer 3 switch or router upstairs (in fact I think it's a 3500 series Catalyst switch now that I think of it - I'd have to look it up to see if that was a layer 3 or not). There are about 21 workstations for students, and five servers running on the 2950's.
 
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