need help designing a business network

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Scott Slagle

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Apr 1, 2013
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hey guys, i have to design a small business computer network. i have 2 buildings, each with 3 offices with about 30 people in each office. the buildings are close enough together that my professor has said they need to be linked up using fiber. What i had figured so far was to subnet each office, then hook them up to their own switch. do the same thing in building two, but have a media converter on each side that will convert the fiber to copper. then somehow hook up two routers for each building for redundancy. just wanted to hear any thoughts/suggestions. thanks.
 
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johnnyq1233

johnnyq1233

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WOW!!
You're talking about 90 PCs in each building and a lot of throughput if all PCs are processing data.
The fiber will handle a lot of data going from building "A" to building "B".
It's the buildings themselves that will be the point where problems could pop up.
What is your redundancy? Copper or another fiber?
Now this small business is it like a sales/marketing setup with common software and business templates?
Please elaborate a bit more on the business that needs connectivity.
 
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okay, i can give better details now. building A has 3 offices (marketing, sales, and shipping) with 16,22, and 8 computers respectively. building B has 2 offices (research and accounting) with 12 and 6 computers each. so i guess i overestimated a little with the 90, but i do have to provide for expansion in my design. building A houses the mail and dns servers, along with a business server. building B has a server has a research server and an accounting server. i would like to design some redundancy into the layout, maybe two routers in each building in case of failure. i would design it all with fiber, but my professor didn't come out and say no fiber, but he recommended cat6. the fiber line connecting the two buildings is something that he also recommended because the 2 building are about 400 meters apart. so if i have to go with all copper except the fiber line, i'm totally new with this stuff, but i did find some media converter switches that will change either copper or fiber to the other. so could i just place one of these switches at either end of the fiber line so it will compatible with the buildings' copper setup? how many switches am i going to need in all; one for each of the 3 offices in building A and one for each of the 2 offices of building B? should the lines from the office switches go directly to the router(s)? and how should i hook up the building-connecting line after its converted to copper? ideally building B should be able to access the DNS and mail servers in building A and also communicate with the network of building A. i know thats a lot, but any help would be great.
 
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bill001g

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Buy small layer 3 switches instead of messing with lots of different boxes. How many actual devices you need will depend on where the wires from the desks terminate to. If they are all in a common room in each building you only need 2.. if you have more rooms you will need more.

You can get switches that you can insert optical interfaces in to match your fiber type. You do not need to run media converters...most media converters are just 2 port switches now days anyhow.

The layer 3 switches allow you to run vlans if you need to run the different offices on different subnets and you can filter between them if necessary. Redundancy gets very tricky in very small offices. You can easily run 2 fiber interfaces on each switch and if you cut a fiber then it can use the other....but this assume they run in different paths fiber cuts are normally because of backhoe and they tend to get all the fibers at the same time. I would just keep a spare switch on hand for other redundancy. You have so few devices it does little good to cable some of them to one switch and some to another, you will end up recabling in case of switch failure anyway.

If you need to provide internet you will also need a router also because one of the few function that a layer 3 switch cannot do that a router can is run NAT.
 
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lukeconft

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Essentially there are many different designs you could go for, but they will largely depend on your needs, your IT staffs understanding of networking and budget.
You need to identify if you have any restrictions on who should be able to access who (for instance, should sales be allowed to communicate with PCs in accounting? Should certain servers only be accessible to certain groups?
Are you planning on using VOIP at any point in the foreseeable future (I would recommend you at least make provision for it)?
Do you have remote workers, VPNs etc?
When you say routers at each office for redundancy, do you mean a router at each office that connects to the internet?
Also, have you had it confirmed that interconnecting your offices with fibre is a ok. If so, will it be terminated in the patching/server/comms room?
Does your office currently have floor ports etc for user computers, that link back to a patching room?
If yes, is this where your servers are located?
What is the budget that you are trying to build this on?

In relation to your initial questions, I wouldn't recommend using 3rd party media converters like that. I would recommend using a Layer 3 switch with SFP adapter slots to interlink the buildings.
The number of switches depends entirely on the budget. If I were to build this for my company, I would be putting 2 48 ports in building 1 and another 48 ports in building 2. This gives plenty of room for expansion, as the cost difference between the 24 and 48 ports is much less than double.
Fibre trunking between switches is fine, but it could get expensive. Your professor is correct, at 400m, your only option is fibre if possible to install or using an ISP to implement a leased line or other WAN solution.

I know it's quite a lot to go through, but laying a good foundation to your network could save you huge amounts of money in the future, as well as preventing failures, security breaches and allowing for a scalable network.

Hope this helps.
 
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Scott Slagle

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Yes they do need Internet, but our designs are supposed to be simplistic, so I was thinking if using 2 routers (for redundancy) in each building. Each office is in its own room, so would it be better to use 2-48port switches one managing 2 different subnets, or one switch per room just in case of failure. Like I say, this is my first networking class so I'm pretty new to all this. Would these first switches then go to the servers individually and to the router? Or would some type of intermediary switch be necessary, I like the idea of using a switch with an adapter to receive the fiber from building b, so should this be used as the intermediary then this switch hook in to the servers and router? Do I have to hook into each server individually or is there a way to interconnect so just one general server connection is necessary.
 
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bill001g

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If this is a school project then it is for you to figure out I guess. Its not like you are asking for a real solution that has many more variables that you have even though of.

For example you want all this fancy redundancy but how are you going to protect a server itself against a switch failure. There are at least 3 ways to solve this and you need to know all these to even decide which design to use.

There are reasons they don't let junior engineers do design. You have to get all the basics before you can think to design networks.

In the real world you make this as simple as you possibly can... the rate of hardware failure using commercial grade equipment is close to zero. A huge part of network design is understanding the difference between 99.99% and 99.999% and what it take to accomplish it and making the cost benefit calculations.
 
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Scott Slagle

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well i just reread part of the description and i'm only allowed to use 8,16, or 24 port switches. so i guess since its 3 different rooms in building A i'll be using 3-24 port switches. one question, though, the switch that handles the fiber from building B, should it be used as an intermediary and my 3 office switches all hook into it?
 
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bill001g

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You can do it that way but it is a unrealistic real world design. Switches are never placed in the end office rooms. The are always placed in IDF closets for a number of reasons. Pretty much all your switches if you even need multiple would reside in that room.

How many switches you have and if you need a intermediate switch is going to be based on building layout.

This is why school assignments tend to have bogus solutions.
 
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