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TOPIC: Help me design a network

Help me design a network 9 years 5 months ago #32131

  • eeepc
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Hello. I need some help designing a network. I hope I've come to the right place. Its purely theoretical at this stage(and likely to remain that way). Suppose, I have a collection of buildings close together, and about 10 buildings, with 4 floors per building, 10 rooms per floor, and 4 PC's per room. Now suppose I want to combine them together in an arrangement that allows each computer to talk to any other computer in the collection of buildings(A giant LAN). Any computer is just as likely to communicate with a computer in the farthest building as a computer right next to it. Each computer must have a minimum of 1Mbps bandwidth(of course, more is better).Naturally I want to get the maximum benefit for the minimum investment. So, what do we do?

Here is my temporary plan:

1. Let there be 1 8-port hub for every two rooms. Thus there are 8 computers per hub. The "uplink" cables from each hub in the building connect to a switch at the bottom floor. Thus a 40+ port switch is required for each building.
2. Connect all the buildings together with another switch?

I'm confused. I know my plan is garbage. I am hoping to hear from wiser and more experienced minds.
Thanks in advance.

Re: Help me design a network 9 years 5 months ago #32135

Ok, here is a few questions I have for you…

1. Money… Like I ask all my clients, how deep are your pockets? Because you can do this the cheap way and have nothing but headaches trouble shooting crapy equipment. Or you can do it the right way..
2. How are the buildings connected?
3. How are the rooms wired? If at all.

You have 160 seats or users per building. 10 buildings in your campus. For a grand total of 1600 seats. You don’t have a giant LAN you have a CAN (Campus Area Network). So using hubs will not cut it.. Hubs create collision domains, which will slow down everything. With a collision domain that large, better off using two cans, string, maybe a rock for attenuation on the string. If your serious about this, you would know this and asking for a minimum of 1Mbps isn’t a consideration where even with hubs the smallest packet size would be going over a 10Mbps connection.

I would say. If you have the budget. I use 48 port switches per floor linked via fiber all the way back to your core network equipment which would some kind of multi bladed layer 3 switch like a 4500 series switch. Then have that switch connected via your medium of choice to your ISP…

Re: Help me design a network 9 years 5 months ago #32139

  • eeepc
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Thanks, Regeth, for your answer. As I said, this is just a theoretical design for a campus network. I don't have any plans at all to do this, and even if I had, I don't think they would allow a totally inexperienced guy like me to set up their network.

Re: Help me design a network 9 years 5 months ago #32140

  • S0lo
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Welcome to eeepc :)

Since your network is large. You better (in fact must) divide it into subnets (or VLANs) and enable routing between them to avoid large scale broadcasts. I also recommend using direct connections (through the walls) from each PC to the building/floor switch without intermediate hubs, this reduces latency and enhances throughput. As mentioned above hubs can cause collisions, so you better avoid them. Here are a few thoughts:

1. Each building obviously needs 4 X 4 X 10 = 160 switch nodes. So you will need switch(s) with at least a total of 160 ports. Either one big switch or multiple switches connected together, or a switch for each floor. Make sure you have at least some extra 10 ports for future changes.

2. Each room should have at least 4 wall sockets connected directly to the switch(s) of each building/floor using Cat6 or Cat5e UTP cables. However, make sure that each cable is no longer than 100 meters. If it's longer, you need to put small bridges/switches in the middle to split those long cables into smaller ones. Longer than 100 meters UTP cables are not reliable.

3. Each building or floor switch should have an uplink (preferably Gb fiber) going to a core switch placed in one of the buildings. The Core switch is a multilayer switch which will do routing between subnets/VLANs. You can ofcourse use a set of routers instead of the core switch. Multilayer switches offer you performance, but routers offer extra services.

4. You better define VLANs instead of physical sub-netting. VLANs are much more flexible.

Hope it gives a start.
Studying CCNP...

Ammar Muqaddas
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Re: Help me design a network 9 years 5 months ago #32143

  • eeepc
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Thanks a lot, S0lo! Your post was really helpful. However, I have a question--

1. I understand why its bad to have one large collision domain. Multiple hosts communicating with each other severely limit the available bandwidth. But why is it bad to have a large broadcast domain?

I am looking up and finding more information about VLAN's from this site and a few books I got from the library. Thanks for the suggestions.
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