Expanding Network: design questions

[mccollums]

FIRST POST: i'm a member of other forums (jet skis, audio/video etc..) and I know basic posts like these usually don't get many reponses... usually takes something pretty spicy and interesting to get alot of replies...sorry, i know some of these questions are lame... but i have to start somewhere .... any answers or help will be appreciated

to make a long story short...i'm the computer guy/net admin\wobbly keyboard tray repair man....of a rapidly growing company... started last year as paper mcse with 37 users........ 14 months later, 77 users and we are expanding to take the whole bottom floor of our building...

Right now we have 2 servers and 5 Cisco 2950s. One server is primarily email and our underused website and the other is a database/image server. images are about 200K, probably accessed 50 times an hour.....My communications closet is near one end of the building so when we expand the network cable would have to be run 150+ feet to each 70+ new cubicles......

I know traffic is the key to this question... but as a general rule of thumb, how many users do you guys normally keep in 1 broadcast domain?

Here's what I was thinking... a small communications closet with 1 3550 EMI and 3 2950s.. add a 3550 EMI and 2950s in my main communication closet... so basically two sides.. have 1 side as VLAN1 and the other VLAN2, with the 3550 gigabit link connecting the two rooms.

VLANs- I will have to buy a 3550 EMI if I do not want to add a Router inbetween the VLANs.. correct? SMI does not do intervlan routing?

subnetting... should I subnet both sides of the VLAN? I have read each VLAN usually has its own subnet

any other suggestions? caveats? books to recommend? cisco switch field manual looks like a winner... other forums?

[t.baranski]

A good message board for general networking questions is:

http://arstechnica.infopop.net/OpenTopic/page?a=frm&s=50009562&f=469092836

[jasgreen]

Hello,

Nothing wrong with the layout of the equipment you are proposing.

However with the VLANs - I would personally keep to a single VLAN, as the number of users you are talking about is small in terms of networks and does not require anything more than a /24 network, although to allow for continued future growth of your network I would recommend utilising a /23 subnet.

[kyhoover]

I would like to ask a more generic question then. I am trying desperately to convince my manager that having a flat network with 1500 nodes on it is simply not a good idea. I know this intuitively, but he is asking for hard and fast data showing why. I'm having a difficult time finding any. Given the size of my network, and the fact that in 2-3 years we will likely be expanding to 2500-3000 users, I need to get some VLANs running ASAP.

Can anyone point me to some good resources that will help me make my case?

[vkasacavage]

The SMI provides routing functionality, so you should not need the EMI. The EMI will give you much more functionality if you need to support multicast routing and other advanced features.

What size to limit a broadcast domain to is always in interesting question, you could look at many different traffic formulas and such, but if you want to keep things simple, limit the number of nodes (users, servers, equipment) to 254. This way you can use a straight class C network to define each VLAN.

You can still split your users into multiple VLANS if you want, but it is generally best to keep it simple. At the size you are stating, you shouldn't have any problems.

As for books, Top Down Network Design by Priscilla Oppenheimer is pretty good for basic design stuff

Hope this helps

[netops01]

All IP routing features require the Enhanced Multilayer Software Image (EMI)

[vkasacavage]

starting in 12.1(11)EA1, SMI provides RIP as well as Static routing

[andyirving]

12.1(11)EA1 SMI has routing (RIP, static) before this release it was a Layer 2 switch only so you would need an external router. The SMI software now allows you to route between VLANs on the switch. EMI costs much more just to add EIGRP (proprietry), OSPF and BGP, is it really worth the extra cash??