VLANs subnets - network newb (long)

Not sure this is the best group to post in, so if not, please direct me to correct one.

I've taken the job of a network admin for a regional library system. I'm new to network admin but am trying best to learn quickly. I was previously in a web admin position when I was (in)voluntarily moved into this job.

The current network is in a working state but needs to be upgraded in many ways. The network sits behind a firewall with 100 or so users, but many more network attached devices. The network is a very simple, flat network NAT'ed inside the firewall with a 192.168.1.x scheme that I foresee running out of addresses in the future. There is one main library headquarters that has the majority of servers, users & devices, then 2 other branches that have 4 or 5 computers, and one more branch that has about 30 network devices. All are connected via fiber by Cisco 3508 & 2950 switches and 2 newer Alcatel switches.

Currently a Windows NT box does DHCP, and authentication for filesharing etc. I will probably replace that box. No real network based applications like Exchange or SQL server. There is a large file server - Snap 4200 that uses the Windows domain for file permissions. There are a few other servers - an AS/400, a SuSE box, and a Win2K server that does A/V and tape backups. No internal DNS, only IP addresses, - WINS? An ISP provides email service.

Not sure the best place to start reconfiguring this network. I know I need the ability to a more add addresses. Would I do this with multiple subnets? Should this be done with VLAN's on the Cisco switches? Do I need to implement internal DNS to make this work? All branches need to be able to access the servers at HQ but not necessarily to each other. Would just expanding to a larger, flat address space be better? I have read some notes from the previous admin regarding cutting down on broadcast traffic, but I don't think the network has congestion problems.

I'm looking for advice and guidance on where to start in re'doing this network!

Thanks, Tanya

Reply to
Tanya L.
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1 network across a wan? seems unusual the though if you have fiber conecting the branches maybe not.

Whats the main problems you trying to solve

Addressing (get a copy of todd lamells CCNA book for a good grounding in subneting)

I would have said use a class b subneted into class c blocks.

Each small building gets 1 block of 254 addresses the main building can either have one block or split the building with lots of hosts into multiple vlans.

You could expand this to have a vlan for publicly usable systems at each site so that you could block any naugty acess to you backoffice systems.

I would use the routers to do DHCP not a windows box.

Dont use a large flat address space!

I think you in over your head its dd that a wan that has the budget for fiber has such odd weekneses. id get help

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Internal DNS is very nice. If you migrate to DNS now, then changing the ip address scheme might be easier. Vlans will cut down on broadcast traffic too (broadcasts stay within whatever vlan they are on,) and each vlan will have it's own subnet. The switch will handle routing between vlans without propagating broadcasts.

Randy R

Reply to
Randy R


Class B subnetted in /24 subnets would be better, maybe not so far off to say class C sized blocks, but technically class C (or was) a range of IP addresses distinct from class B.

(and TCP questions should go to comp.protocols.tcp-ip, even when they are carried over ethernet.)


-- glen

Reply to
glen herrmannsfeldt


Your quite right about class B as a /24

But geting your adressing right is the first step to a better network design.

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