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Windows 2003, 2 x DHCP, VoIP, 2 x Subnets, 2 x Routers, Proper Planning!

Posted on 2006-07-19
Medium Priority
Last Modified: 2010-05-18
I'm new to VoIP and Windows 2003 but i do wanted to give the following setup a shot so i've planned it appropriately however i have a few questions which i'm not sure about and was hoping that someone could help out, so here is the deal:
Internet-----DSL/Router------Router-----------Windows 2003, DHCP, DNS, AD, DC, File Server
                                         |       |               (1 x NIC,,, gw
                                         |       |               (DNS, FW to my ISPs DNS server IPs)
Windows XP SP2(4 x PCs)---|       |               (DHCP Range
                                         |       |-----------3COM NBX100 VoIP Base System
 XEROX Copier----------------|       |
                                         |       10mbps Switch-----------VoIP Phones (4 x phones)
 Canon Copier-----------------|      
                                 10/100mbps Switch------------------VoIP phones (7 x phones)
                                 10/100/1000Gbps Switch-------------Windows XP Pro SP2 (5 x PCs)  
My Questions are:
1. Can i Have 2 x DHCP running, one is a NETGEAR Router (,, the other is the Windows 2003 with parameters mentioned above?
2. Can i Authorize the Windows 2003 to be the default DHCP for the Windows XP machines and have the NETGEAR lease IPs for the VoIP phones?
3. What would the routing table look like on the Windows 2003 machine or how should i set it up. Do i use the Remote access and routing Tools?
4. Is there anything in the setup listed above looking wrong or could be improved.
5. Regarding the two printers i was thinking to set reserved addresses in the DHCP Scope in Windows 2003 say and
6. Reading through other posts i saw that there are some internet connectivity issues when i don't have the gateway on the say segment as well as no ping, isn't that a routing table issue?
7. The reason why i've planned it this way is because of DHCP failover - if the Windows machine goes down then the phones will be still functional running of the NETGEAR router on a separate IP range.

Please let me know when you get a chance. Thanks.
Question by:vaworx
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LVL 51

Accepted Solution

Netman66 earned 2000 total points
ID: 17143052
1) No, not really.  As long as they are both on the same segment then either one will give out IP addresses depending on what replies first.
2) No.  You'll need to isolate the clients before they can deal only with one DHCP device.
3) See comments at the end.
4) Yes and yes.
5) Good.
6) Depends on what gateway you're using.
7) Understand and good idea.

Now, for comments on point 3 and 4.

Point 3:  The routing table will build itself.  In your scenario as outlined above there is no way to prevent client and phones from getting addresses from either device.

Point 4:  Here is what I would do....

Internet-----DSL/Router------Router-----      Switch             ------Windows 2003, DHCP, DNS, AD, DC, File Server  ---------- 10/100/1000Gbps Switch
                                                                    |                        (1 x NIC,,, gw          |
                                                                    |                        (DNS, FW to my ISPs DNS server IPs)             |
                                                                    |                        (DHCP Range                                      |
                                                                    |                        (RRAS configured as basic firewall)                                    |
                                                                    |                                                                                                              |        
                                                                    |-----------3COM NBX100 VoIP Base System                                                 |--Windows XP Pro SP2 (5 x PCs)  
                                                                    |                                                                                                              |--Windows XP SP2(4 x PCs)
                                                                    |-----------VoIP Phones (11 x phones)                                                          |--Canon Copier
                                                                                                                                                                                    |--XEROX Copier
This way your phones will pickup address from the Netgear (make sure they are on the same subnet as the rest, just a higher scope.
Your PCs will get addresses from the server.
Was there a reason to separate the W2k PCs, 7 phones and 2 copiers in your drawing?

Author Comment

ID: 17143277
Thank you for the fast reply. The reason why some PC and phones are separated from the rest is because they are two distant locations ( 2 office locations about 300ft away from each other). I would need to run separate cables for voice and data from the second office where the 3COM NBX100 is to the main office where the Win 2k3 server is. I want to make it as rational as i can with less cables, not that spending on cables is an issue with .10/ft :D. In details my idea is this:

Main office:                                                                                        
|__|__|__|__|__|__|___|____10/100/1000GBps Switch
Ph Ph Ph Ph Ph Ph Ph  Copier0                           |                                                 Second Office:         WAN Port
|__|__|__|__|__|__|____|___10/100Mbps Switch----------------------------NETGEAR 10/100Mbps Router---DSL/Router
                                                                                                              |   |   |   |        |           |           |
                                                                                                              PC PC PC PC  Copier1     |       Internet
                                                                                   3COM NBX100------10MBps Switch-----------|
                                                                                                                |    |   |   |
                                                                                                                Ph Ph Ph Ph

Author Comment

ID: 17151573
please advise
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Author Comment

ID: 17151595
1. How would the two subents see each other since the Windows 2003 Server is connected to the network using only 1 NIC with a static ip on it
2. How would it see the Gateway which is on a separate subnet range
3. I want to install an application that comes with the 3COM NBX100 on the Windows XP machines that emulates phones as well as the control panel for the Base Station has to be accessible from the XP machines so that the users can add new employee extensions and manipulate it online which would look like so:

PC------------------IE http:\\ (the NBX100 address)

4. How would these networks talk to each other, Do i have to set routing on the NETGEAR Router somehow or that would be a servie running on the Windows 2003 Server. I already tested the above mentioned situation in my place with a linksys router and the server but the networks don't talk to each other. Not only that but the Server does not even connect to the internet.

I assume there is something wrong with the routing but i'm not sure where and how to set it up. Please advise....
LVL 51

Expert Comment

ID: 17153075
I haven't forgotten you.

I'm trying to make sense of your last picture.

I think you're confusing things by using routers for each building - that unnecessary.

Place a switch at each location and you can join them using a crossover cable.  Since the last switch will share 1 port connection, then if you can afford it you should use GB switches - this will mean the last building will share a duplexed GB pipe (good).

If you run past 300ft, then copper isn't going to be reliable.  You may need to use a tranceiver on each end and fiber in the middle.  Alternatively, you can use 2 fiber ready switches and Gbics to daisy-chain them to the main office.

By keeping each building on the same LAN segment, you save a bit of work in subnetting and working out the bugs because of it.

Author Comment

ID: 17157874
Thank you for the reply again,
That would be the easiest thing to do but as i've mentioned in the previous post the main reason why i want to have 2 X DHCP on the same network is because of DHCP failover which is more of a - if the Windows 2003 box goes down that's OK, because the NETGEAR would still lease addresses to the VoIP phones and that would be less down time for the business in general. I am not using 2 x NIC on the server because if it goes down there will be no connection for the Windows XP machines wheras in this case when there is only one NIC only the domain portion won't work other than that the machines will still lease an ip from the NETGEAR DHCP. The things that i'm not quite sure about is if the Windows 2003 box will in fact do proper routing with one NIC so that the 2 x Subnets will in fact talk to each other. I'm not good at explaining stuff but the idea is there. As we say here it all comes down to CAN or NO CAN do that kine of setup :D. If not, what would your recommendation be given the fact that having the phones working at all times is crucial to that company.

Thanks again for all your help.
LVL 51

Expert Comment

ID: 17158117
I think you'll find the phones will continue to work since they have a lease on their IP addresses (by default 8 days) so it would be a very slim chance that the server would go offline around the time they require a refreshed IP.

All you would have to do at that point would be turn on DHCP on the router and you're good to go.  Not a long process at all.

With respect to routing, by subnetting things you actually make things a bit more difficult since broadcasts do not pass the routers so DHCP would then have to come from a local source - which also means the clients probably won't register in DNS also.  NetBIOS traffic will also be affected - which means that browsing for a resource across the router won't yield any results and the Master browser (the server) would not know anything about machines outside it's own router.

I would try to keep it all on one network - you'll make your life a lot easier.


Author Comment

ID: 17158997
I think i finally found the answer to my question. It looks like i need to setup what is called a one-armed router in order to manipulate the setup that i wanted at the first place:

I'm still reading on it so i'm gonna come back and probably post a manual if i have succeeded in my setup. If you have any comments on that feel free to post here at any time. I'm going to have to perform the setup tomorrow so i hope it works as planned. It will be another sleepless night until i figure this one out...

Author Comment

ID: 17159009
Here is some more info, i guess 2 X DHCP was misleading in fact looking at all the NFO it all comes down to setting up DHCP on the Windows 2003 only and having the NETGEAR Router setup as gateway with DHCP disabled then create two separate scopes for and on the Win2k3.

Does that sound about right so far?....
LVL 51

Expert Comment

ID: 17159716
If you're still thinking the remote offices will connect via router then that trick won't work.  Besides, I don't think these consumer routers allow more than one IP on an interface - and even if it did, it wouldn't do what you are looking to do.

If you're simply looking to separate the phone and date traffic then each switch in your solution should be capable of VLANs.  Set it up the way I mentioned above where the switches connect each office, then VLAN off the number of phone ports you need plus a few extra in case you need them later.

DHCP can then be setup to handle both subnets.


Author Comment

ID: 17181450
It actually turned out to be working a OK:

In my NETGEAR router i've added the Win2k3 Server as static router, on the Win2k3 machine i've installed Routing and Remote Access(which actually comes by default all you have to do is configure it), both my switches are VLAN enabled so that wasn't a problem and now both machines ping each other and can logon to the domain. I'm still testing to make sure how is everything working but i guess as far as DHCP lease goes i'll know for sure after 8 days. Of course the Win2k3 messed up the DHCP domain and added as default DNS suffix so i'm still working on that. From what i've read so far i have to remove the service and install it again to make sure that it will be working a OK. I'll keep everyone posted on that.

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