Subnetting existing network

I have an existing network comprised of office user computers and production computers/PLC's on the same subnet.  My goal is to isolate the office machines and put them on a separate subnet as to not be subjected to all the data collection bandwidth usage from the production equipment.  My network is setup as - 254, subnet   I want to keep the production equipment untouched as most are static IP's, but the office users are DHCP so would like to setup new subnet for them.  My question is; what new IP schema should I use for my office environment, ie: - 254 subnet  Also, the new router that I have to buy to make this happen, what IP forwarding to the old router do I need to do to make this seamless so my users can still see the production equipment?  And lastly, I obviously have to change the DHCP scope range on the server to hand out the new IP's. (thats not really a question, just thinkin' out loud).  Any help or input is greatly appreciated.
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Mick FinleyNetwork EngineerCommented:
Vlans would be the best way to do this.  Are your present switches capable of VLANS?

I honestly doesnt matter what IP subnet you use just as long as you stick with the private ranges.  I use a mix of 192.168.x.x 172.20.x.x and 10.x.x.x for ease of recognition.  the router you get you'll want it to be able to support both LANs, it will need to support VLANS, which would then mean your switches will need to support VLANS.

Once you get the hang of it, VLANs are really simple.  

Id check on the sonicwall TZ line, not sure if they are up to the task you are after.


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Ron MalmsteadInformation Services ManagerCommented:
It really depends on the existing equipment you have... you may not even need a new router if you have a higher end ...managed switch.

As Keving pointed out, it really doesn't matter what you choose for IP range.

See attached... this is basically what you are talking about doing.

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xuserx2000, wouldn't you create a double NAT'd environment for the subnet?

I've ran into issues with that.

Here was what I was thinking:

Ron MalmsteadInformation Services ManagerCommented:
I've done this both ways....
VLAN is the best way though.  Not because of nat, but because of increased potential for bottlenecking.
dynamictechincAuthor Commented:
Thanks for the replies!  I've been researching the topic for vlans and loving the concept.  To answer the question thrown back at me, all of our switches are simple unmanaged, BUT recently we bought some production machine that came with a couple of Cisco managed switches and remember the contractor telling me about port assignments on them but he didnt know how to set it up.  I have a call in to him right now to find out if these are layer 3 switches.  As I move forward with vlans, I am thinking VLAN1 for production and their servers and VLAN2 for office and their server.  Keep in mind I still need some users in VLAN2 to access data on a VLAN1 server, and the way I understand it a layer 3 switch will allow me to set this up.  Is that right or do I do it thru the router?  If so, how difficult is it through the switch to setup, or the router?
It is a pretty easy process, you'll want to do all routing on the firewall in your size environment.

What model # switches do you have most cisco are capable.
Ron MalmsteadInformation Services ManagerCommented:
If it's a cisco switch, ...there are a mountain of examples out there.
Can you tell us the model of the switch ?
yes, i agree with experts here...

one option is segmentation
you split your current n/w to 2 subnets ie to

1. ie you get hosts with - and subnet mask
2. - hosts - and subnet mask

further down you mentioned that you have some new cisco boxes, anyways. its easy to configure VLAN and then add VLAN filter to control inter-VLAN communications...

let us all know, eager to help you.

Istvan KalmarHead of IT Security Division Commented:

If you buy CISCO asa you able to make L2 firewall

Please refer this page:

dynamictechincAuthor Commented:
I am working to get you guys the model numbers of all the switches that will be used so bare with me, just trying to put out other fires the last few days.  Thanks to everyone for replying.  I will supply the information soon I hope.
dynamictechincAuthor Commented:
update: We have installed the new router (Cisco 2821), as well as a new switch (Cisco 2960G).  I've decided to go the VLAN route and now in the process of mapping out the plan.  Still not sure how to configure the router to handle the inter-vlan communication, but i'm sure i can find all sorts of docs to figure it out.  Thanks to everyone that replied!
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