two domains on the same flat network

We have an office with an sbs 2003 domain controller, we will call this domain1 and the server name is server01. We are closing another office but want to move it's server, another domain controller for that office to our current location. This is an SBS2011 box and the server name is server01. This is domain2.

So can we have the two domain controllers for our two different domains run on the same network.  Domain1 is the SBS2003 box, server01.local.domain1 and it's ip address is We add Domain2, SBS20011 box, server01.local.domain2 to our existing network and make it's ip Of course different workstations are members of each domain.

Will we have any issues as a result of running two different domain controllers over the same network? Will the server names cause a problem since they both are server01 but specific to their own domains?  We don't need the two to talk to each other, just use the same infrastructure.
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Cris HannaSr IT Support EngineerCommented:
Is the goal to share a common internet access?   You can't have both servers, which happen to have the same name and the same IP scheme on the same network...DHCP will be a night mare, DNS will be a nightmare...just ugly

At a minimum, these networks need to be separated by routers
Keith AlabasterEnterprise ArchitectCommented:
Even then, I could see issues occuring in all sorts of ways. I am hoping that they are NOT both called server01and that this is just the names given by the asker as examples within the question.
holcomb_frankAuthor Commented:

The goal would be to have both staffs working in the same building.......and yes be able to share the internet connection. As you know I can't rename the DC.......  seperated by routers??
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holcomb_frankAuthor Commented:
yes both servers are named server01 with different domain names due to the two orginal office locations that are not being combined?
You can't have two server with the same name on the same broadcast segment. What you can do is:
Install an managed switch, then declare two isolated vlan. That will resolve the network problem, but will also cut any comm betwen the 2 domains (like two separated switch).
For the internet output you need a good firewall that is capable to deny all trafic from on server to other.
If not: rename one server, then put all pc on the same network. Domain 1 will use DHCP, domain 2 will use fixed IP settings. You can put both on DHCP but you need to have a secondary zone on the other domain.

I already had this situation, but not the same computer/domain name.

Cris HannaSr IT Support EngineerCommented:
It's important to understand that if you maintain 2 separate domains, with a single internet connection, that you will be unable to port forward to both servers on the same you'd have to decide...which server gets Port 25 and Port 443 forwarded to it.

If this were my situation, I would get a second internet connection.  Then buy a dual WAN, dual LAN firewall router.   Both networks would be completely isolated from each other and function just like they did before.

Otherwise you'll have to turn of DHCP on one of the servers and you still have the issue with remote access and inbound email not working

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holcomb_frankAuthor Commented:
Ok... we got the other server in house now and it's different then we were told.  Actually the original dc is named server01.domain01.local. The other server, which we have not set up yet is actually named server03.domain.local. " Domain" is the same on both servers so the distinction is domain vs. domain01.

Given that..... do you still see the same issues now. The servers actually have two different names. They would just be using similar ip schemes. 10.1.x.x for both.

Again the main goal here is to share the internet connection between both domains. There is no port issues that i can see....all connections to this network are through a VPN.

Could this work without messing up either server.??
Cris HannaSr IT Support EngineerCommented:
so both domains share the same domain.local domainname?  I understand that they are actually unique domains but if they have the same domainname...DNS is going to be the problem as well DHCP...The only way they get pointed to the correct location is static DNS addresses for each client.    

You still haven't indicated how you're going to deal with mail inbound with 1 external IP
holcomb_frankAuthor Commented:

Mail is not an issue for this's not hosted in house. It's all webemail.

The dc's are server01.bob.local and they don't share the same name ???

What do you think...??   I can turn off dhcp on the original dc, everything is static on that box.....and the only reason for internet on that box would be updates.
Cris HannaSr IT Support EngineerCommented:
I think you can make this work for the short term, but the long term goal here should be one network with one domain.
holcomb_frankAuthor Commented:

The only thing I can see happening right now is a limited amount of IP addresses due to the same 10.1.1.x segment will be shared by both servers.

Dc old and Dc new    there is going to be about 25 workstations total so I'm not to concerned about the IP's but that was my biggest question now.

It would seem that the DC names are different enough that it shouldn't be an issue....each workstation will go to it's appropriate dc by it's membership right??

I agree....long term planning is to combine these two sites if it stays this way.
Keith AlabasterEnterprise ArchitectCommented:
Maybe I am just too old now to look long-term at workarounds but I guess you are not in a position to be overly choosy at the moment.

I think you will have some some strange issues to overcome with naming and services etc but as you don't seem to have many choices........
Cris HannaSr IT Support EngineerCommented:
Personally I'd put them on different IP ranges...really easy to do with SBS 2011
Keith AlabasterEnterprise ArchitectCommented:
holcomb_frankAuthor Commented:

And still use the same gateway ??
Cris HannaSr IT Support EngineerCommented:
You'd have to change the subnet to and should be able to get to the gateway
holcomb_frankAuthor Commented:
Sorry for the delay....busy, busy...

Ok...what i did was log into the existing SBS2003 box and i turned off dhcp all together. Then I selected a range of Ip's that would give this group everything they needed including their printers and everyone is now on a static ip address with in this specific range. All the stations are running fine and not having any issues at this point. Then we brought in the SBS2011 box and set it up with Dhcp and set up the scope to exclude the specific range that the other network is using and of course reserved the ips of each server and their router so there would be no issues there. Each server is still running it's own DNS and Wins for that matter.

Both servers are up and working on the same network. At this point all the workstations are still on the original SBS2003 box, but as we set up the SBS2011 network all the workstations are connecting without any issues. So far so good and this was Tuesday of last week.

I can remote back and fourth within in the two servers from one to another or from a workstation to either server with the correct credentials.

No one is complaining of network issues or this is good for us.

Both servers have access to the network printers and gateway. Since email is all web based at this time, and no one uses RWW or anything like that. Port forwarding has not been an issue. We connect to our office location using a VPN and then remote directly to the server. I can do this on both servers right now as well.

Keeping my fingers far this is working good for me.
holcomb_frankAuthor Commented:
Thanks for everyone for feedback.... so far so good.
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