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IP address conflict using office wireless network with DHCP

Posted on 2011-03-24
Medium Priority
Last Modified: 2012-05-11
I work in a small office that has a Windows 2003 server and a wireless network.  This setup has worked fine for a long time, but as of a couple days ago I can no longer connect to our server internally over the wireless network.  (I can connect when I am hardwired and also from home through VPN)

I noticed that the server has assigned itself an IP address for PPP adapter RAS server (Dial-In) Interface (, and it is the same IP address that was assigned to me through DHCP.  Should I modify the router so that the DHCP addresses start at  I'm not sure how the PPP adapter RAS server IP address was assigned, so I don't know if that will change or if that also is based on the DHCP addresses.

Thanks in advance!
Question by:rhaak
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Expert Comment

ID: 35208004
You should assign IP Address in the server manually and you should exclude that chunk of ip addresses from dhcp scope...
LVL 11

Expert Comment

ID: 35208152
I agree with Shubhanshu post....first of all you should always assign a static IP address to your server.  It should not get the address from the Router.

If this was my network I would assign a static IP to the server something low under the the 100 range...example  Then start the DHCP on the router to something like and make sure you have enough IP addresses to handle the amount of computers attaching to it.  

Author Comment

ID: 35208258
The server (LAN) does have its own static IP address, and DHCP cannot use that address.  It's the "PPP adapter RAS Server (Dial In) Interface" at the server that has the problem.  I'm not sure where to assign that IP address or how it got set?
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Expert Comment

ID: 35208271
You need to define the range of IP addresses for the clients and make sure that the ip address of the server is out of from the defined range.

Author Comment

ID: 35208371
When I run ipconfig at the server, it lists 2 separate address:
1)  Ethernet adapter Server Local Area Connection (I understand how to assign that and that address is not in the current DHCP range)
2)  PPP adapter RAS Server (Dial In) Interface (I don't know how to assign this and if it's a static or dynamic address)

If the latter is definitely a static IP address I will modify the DHCP range so that it doesn't include that address, but the issue is I don't understand how it gets assigned or where to modify it and if it can change in the future.
LVL 14

Expert Comment

ID: 35211199
you should modify this by setting reserved ip address in dhcp server

you can change router ip address in sites and services in Active directory


LVL 11

Accepted Solution

Patmac951 earned 2000 total points
ID: 35211288

Without taking credit for this check out this experts-exchange link it will tell you how to assign specific IP addresses from your RAS pool.


Author Comment

ID: 35216157
Thanks for the link, that's exactly the instructions I needed.  Unfortunately I did modify the RAS server to use a static IP pool, but now when I run ipconfig at the server, there is no IP address for PPP adapter RAS Server (Dial In) Interface and therefore I can't VPN.  I restarted RAS, and I rebooted the server, but neither helped.  I also tried putting the RAS server back to DHCP but that didn't do anything.  Do you know how I can tell the server to assign an IP address to the RAS server?
LVL 11

Expert Comment

ID: 35217189

The RAS server requires DHCP to assign the IP address and it will always use the first logical IP address from within your RAS pool.  For example if your RAS pool was set for -  This would give you 30 valid IP addresses for your VPN users and would be the IP for your RAS server.

So just make sure the range of  RAS pool of IP addresses does not conflict with any other IP addresses on your network especially the DHCP range on your router.  Make sure the RAS pool IP address range does not conflict with the DHCP range on your router.

Author Closing Comment

ID: 35258061
This was exactly the link I needed and everything is working now.  Thank you!

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