Cisco Support Community
Showing results for 
Search instead for 
Did you mean: 

Welcome to Cisco Support Community. We would love to have your feedback.

For an introduction to the new site, click here. If you'd prefer to explore, try our test area to get started. And see here for current known issues.

New Member

Help with Network Design

Hi NetPros. I need your help.

I have to design a LAN network for about 4.000 users. I planned to use Cisco Catalyst 6500 in the core and Catalyst 3550 in the access, but it could be any other option (no money problem).

The problem is that it's the biggest network I've had to implement, and I don't know how to define the network topology.

Any advice will be welcome.

Thanks and regards.

New Member

Re: Help with Network Design

Is the 4,000 users going to be all at one site? IE, is this just a LAN design ?

New Member

Re: Help with Network Design

Yes. They all will be at the same site, and any user must connect with each other.

There will be 30 servers too.

New Member

Re: Help with Network Design

How many access closets will you have and how many users per access closet? I would base my choice of using stackables or modular switches on this.

For the core, I think the 6500 series (probably a 6509) would be good. Since you say money is not a problem, I would populate with redundant Supervisor Engines. For the 30 servers, will you be running GigE to them or just Fast Ethernet?

Do you have any plans for redundancy built in to your design. It's an expensive option, but you may look at putting in dual 6509's and then running your access closets to each of these.

Hope this helps.


New Member

Re: Help with Network Design

I would like to divide 4.000 users in groups of 253, to create 16 C-class subnets. For the physical situation of the users (long site), I think stackable and separate switches are the best option.

The servers will be in GigEth, since all users must access to them.

I think redundancy could be very interesting, but I don't know how to implement it.

New Member

Re: Help with Network Design

I'm intrigued by the dichotomy of your objectives to 1.) Create "x" number of class C subnets, and 2.) "Interesting" Redundancy. Why is no. 1 an objective at all? Why is no. 2 only "interesting"? Why must all servers have a gig connection?-- just because all users must have access to them? Really? Hopefully you have your reasons.

It is tough to offer concrete advice with the limited information you've provided.

You need to define your priorities and identify assumptions. I strongly recommend you frame these in terms of your customers' expectations.

What are some of your business objectives? Are you a manufacturing firm or a healthcare institution? What kind of applications will be accessed? Why is the expectation for availability? Can you create a simple flowchart that illustrates how data will need to move around your network? Do you have some metrics to assist you, or are you shooting from the hip?

It must be nice to have no budget limitations, but I suspect you'll wind up building a aircraft carrier when you only need a battleship. Just remember, the real cost to your organization is realized in terms of worker productivity -- you may spend a total of $50,000 or $500,000 on network infrastructure, but what will it cost the organization if the 4,000 clients can't access your primary CRM application?

I guess the whole point of my post is that you have to focus on the business fundamentals first before you're ready to move on to the technical challenges. Remember, routers, switches, access points, etc. -- these are all merely tools. Define what you need to build before you go shopping for a hammer.


New Member

Re: Help with Network Design

Very nice post Greg!

In order to do a good job, you definitly will need to understand and perform the tasks outlined above. Also, did these 4000 users show up over night, or will you have to incorporate legacy systems and infrastructure.

Sure you can fit 253 users on a class C network, but you should design a efficient network with room to grow and not too large of a broadcast domain for any segment. Cisco has recommendations and so does the different OS manufactureres. You would assume that the business will most likely expand over time and so will its staffing and computing needs. Mapping out a current and future IP addressing scheme is just one more task.

As far as the design goes, there really are only a few options for the physical layer and you should just follow Cisco's best practices and recommendations.

For hardware, you are probably on the right track for your core, but what about distribution and access points? Do you need them, or can you collapse them into one box. The physical layout of the facility will help answer those questions. After a site visit, some choices will be elimenated.

When you get down to the nitty gritty of implementation, the link below will help with some configuration options to make your design more robust.

I know that this post is fairly vague, but it sounds like that is just about where you are in the process. Good luck.