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New Member

LAN Setup

Hey guys/gals,

I'm looking for some feedback on how I should go about setting up my lan. Currently have a bunch of 3com switches connected via Matrix, and Fiber. They are being replaced with Catalyst 3550s. My questions is:

What is the best way to set these switches up?

I was thinking the following. All workstations are going to be set to 10mbit half duplex, with spanning tree off. Servers will be set with 100mbit full duplex flow control, spanning tree off. Is this okay, if not why? Should I configure everything like the servers?

2nd, I have two 3550 with fiber modules. I should connect these full duplex, flow controle, with spanning tree enabled correct?

3rd, I will have one 3com switch left, what is the best way to link the switch to the 3550? I don't think one single 100mbit via crossover will cut it.

Hope someone can help, as I'm quite new to networking. Any feedback good/bad appreciated. Any howto docs, or links greatly appreciated!

2 ACCEPTED SOLUTIONS

Accepted Solutions
Cisco Employee

Re: LAN Setup

There are a multitude of ways to go about designing a network, and there are certainly many ways that are equally valid. From my own experience, I would recommend the following:

- Configure your workstation ports to autonegotiate speed and duplex. This way you can have ports negotiate themselved depending on the NIC that is attached. This way, having a mixture of 10, 100, full, and half duplex NICs won't be a pain to manage. I would not recommend using half duplex if the NICs support full duplex, as this will result in collisions that can cause application and/or network latency.

- Since servers tend to be much more static than workstations, I certainly agree with hardcoding the speed and duplex.

- Since servers and workstations are both host ports, you should definitely configure spanning-tree PortFast on those ports.

- As for the uplinks, what you have in mind is the best way.

- For the 3com switch, I am not sure of it's capabilities, but if it supports some form of channeling, you may want to configure an etherchannel between the two switches. The following link details the configuration steps for an Etherchannel:

http://www.cisco.com/univercd/cc/td/doc/product/lan/c3550/1214ea1/3550scg/swethchl.htm

The following link should help as well.

Designing Switched LAN Internetworks

http://www.cisco.com/univercd/cc/td/doc/cisintwk/idg4/nd2012.htm

Cisco Employee

Re: LAN Setup

The only difference between half duplex and full duplex is that with full duplex you can transmit and receive data simultaneously. With Half-Duplex, you can either send or receive data, but not both at the same time. The use of full-duplex vs. half-duplex has no bearing on whether the data reaches its destination or not.

Spanning tree PortFast causes a port to enter the spanning tree forwarding state immediately, bypassing the listening and learning states. This way switch ports connected to a single workstation or server allow those devices to connect to the network immediately, instead of waiting for the port to transition from the listening and learning states to the forwarding state.

4 REPLIES
Cisco Employee

Re: LAN Setup

There are a multitude of ways to go about designing a network, and there are certainly many ways that are equally valid. From my own experience, I would recommend the following:

- Configure your workstation ports to autonegotiate speed and duplex. This way you can have ports negotiate themselved depending on the NIC that is attached. This way, having a mixture of 10, 100, full, and half duplex NICs won't be a pain to manage. I would not recommend using half duplex if the NICs support full duplex, as this will result in collisions that can cause application and/or network latency.

- Since servers tend to be much more static than workstations, I certainly agree with hardcoding the speed and duplex.

- Since servers and workstations are both host ports, you should definitely configure spanning-tree PortFast on those ports.

- As for the uplinks, what you have in mind is the best way.

- For the 3com switch, I am not sure of it's capabilities, but if it supports some form of channeling, you may want to configure an etherchannel between the two switches. The following link details the configuration steps for an Etherchannel:

http://www.cisco.com/univercd/cc/td/doc/product/lan/c3550/1214ea1/3550scg/swethchl.htm

The following link should help as well.

Designing Switched LAN Internetworks

http://www.cisco.com/univercd/cc/td/doc/cisintwk/idg4/nd2012.htm

New Member

Re: LAN Setup

Thanks for the reply.

Basically not having it auto isn't the problem. I need to force a standard, because I need to know if there is a problem with the link. I was under the impression that half duplex will guarentee the packets to reach their destination, where as full duplex could cause dropped packets. But then am I correct to assume that flow control will take care of that worry for me?

Also I though PortFast was a different feature not part of STP. However I do have them emabled for the workstations, and servers.

Also this is a very controlled environment, nothing can be changed unless IT is involved.

Cisco Employee

Re: LAN Setup

The only difference between half duplex and full duplex is that with full duplex you can transmit and receive data simultaneously. With Half-Duplex, you can either send or receive data, but not both at the same time. The use of full-duplex vs. half-duplex has no bearing on whether the data reaches its destination or not.

Spanning tree PortFast causes a port to enter the spanning tree forwarding state immediately, bypassing the listening and learning states. This way switch ports connected to a single workstation or server allow those devices to connect to the network immediately, instead of waiting for the port to transition from the listening and learning states to the forwarding state.

New Member

Re: LAN Setup

You should take advantage of what the cisco switches offer you. Each port can run at 100mb with full duplex so my suggestion is to use this with the workstations also. With full duplex you will never have any collisions and packets wont be dropped. Cisco recommends not using auto but just by setting it manually.

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