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Slow Lan Performance on a Switched netwo

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Recently we put up 8 Catalyst 2900 XL switches to replace our old hubs. We disabled Spanning Tree protocol on all switches except the one connecting our servers. After the change our LAN performance slowed down to a crawl. WE are using a Netware 4.11 server with 2 NICS. All out machines use 3COM cards. We configured all workstation ports to half duplex 10MBps. After this, the speed improved but its still not as fast as before.
What are we doing wrong?
Thanks for your help.

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Slow Lan Performance on a Switched netwo

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You didn’t specify what card you use. If it is capable of 100mb then that may be your problem. Your network may have been running at the higher speed. You should allow your cards and switches to auto-negotiate the speed. If that doesn’t help, set the speed of both to the highest the cards will go with full duplex turned on. Hope this helps.

Slow Lan Performance on a Switched netwo

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Slow Lan Performance on a Switched netwo

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Here is some more info about emartinezm’s network:

The NICS are all 3COM 3C90X, both at the server and at the workstations. 7 of the switches are connected to the same switch as the servers using crosover cables. l disabled full duplex in all ports after reading at the Novell site that some 3COM cards have problems negotiating with Cisco equipment. The Catalysts are using IOS version 12. We are running using the IPX protocol.

Slow Lan Performance on a Switched netwo

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Slow Lan Performance on a Switched netwo

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I think you are creating a huge collision domain in your network… They are all converging at the switch where the servers are physically connected to…

If you have flexibility in the design you may want to do this over the weekend…

Have a tiered approach… A triangle on it’s point…

A-A-A A-A
\ /
B — B
\ /
C

A are your client network switches, hopefully all of your traffic is in-house and doesn’t need to go out, if it does, then go to Bis the traffic is on the other side of A… If not then and only then do they go to C… This segments the networks well and allows for scalability in the future where as the seven tied to one would defintitely need fixing later…

Just a thought…

I would keep the users at 10M and the server connections at 100… If the users need or want 100, then there should be multiple 100M links between the B and C levels…

I hope this gives you some food for thought…

Johnny

Slow Lan Performance on a Switched netwo

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Slow Lan Performance on a Switched netwo

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YOU NEED A SNIFFER! What’s on the network? Check for any ICMP messages. Check out http://www.netanalysis.org. Also try to minimize any amount of multicasts. But basically… you need to sniff your network to root out the problem. You’ll just be guessing ’till you do.

Hope this helps.
Stan 🙂

Slow Lan Performance on a Switched netwo

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Slow Lan Performance on a Switched netwo

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The network is set like Saber_21 says. The problem was our 3COM NICs not autonegotiating correctly with the switches. We configured the switches and the servers explicitly to use duplex 100MBps. Now the network is very, very fast!
Thanks to all for your help. emartinez should close this very soon.

Slow Lan Performance on a Switched netwo

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Slow Lan Performance on a Switched netwo

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One thing for you to try is setting the switch ports that serve the NIC’s in your server to half-duplex. It may be that Netware is initializing your NIC’s at 100/half.

Antother thing I would try is to turn spanning tree on if you have the switches hooked together. The following is from the Cisco web site and might help you understand what happens if you do not have spanning tree on.

“When you create fault-tolerant internetworks, you must have a loop-free path between all nodes in a network. The spanning-tree algorithm calculates the best
loop-free path throughout a switched network. Switches send and receive spanning-tree frames at regular intervals. The switches do not forward these frames, but
use the frames to construct a loop-free path.

Multiple active paths between stations cause loops in the network. If a loop exists in the network, hosts might receive duplicate messages. In addition, switches might
learn host Media Access Control (MAC) addresses on multiple switchports. These conditi

Slow Lan Performance on a Switched netwo

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Slow Lan Performance on a Switched netwo

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First, there are alot of good suggestions already, and spantree should definitely be turned on. You must also set each interface, that connects to a server or end user, with portfast enabled. This will allow each interface to bypass the spantree algorithm. Make sure you do NOT enable portfast on switch uplinks!!
Your problem may also be with existing bottlenecks in your network, adding switches will not necessarily releive that type of congestion. Using a sniffer on your uplinks will determinethe utilization and you should be able to track down congestion issues.
Hope this helps,
Regards
Steve

Slow Lan Performance on a Switched netwo

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