Unidentified Network

FriendlyT used Ask the Experts™

I have a problem at an office network.

The network has the following:

1. A Windows 2008 R2 Server running as the DHCP host
- IP address is
- DCHP range is 100 - 200

2. Unmanaged network switch

3. Modem Router

I was called in to update the password on the modem as it was changed with the internet service provider. They did not know what the log in information was for the modem and it was not the default so I reset the modem and re entered the internet service provider details.

I could connect to the internet using my laptop plugged straight into the modem router but when I plug the router into the switch and try to get to internet by plugging into the switch it does not work.

The network tries to identify and fails. The laptop reports it is an unidentified network.

Question: How can I get my laptop to access the internet when plugged into the switch?

Does the modem need to be set as a DHCP Server, DHCP Relay or disable?

Is there anything else that needs to configured in the modem?
Watch Question

Do more with

Expert Office
EXPERT OFFICE® is a registered trademark of EXPERTS EXCHANGE®

If you connected the laptop to the modem, then disconnected and connected the router to the modem, it's not going to work. You first have to power cycle the modem and router (unplug their power for a minute and plug them back in). Then give the modem another minute to be fully online, then connect the WAN port of the router to the modem.

For this to work, you must also be sure that the router's Internet (or WAN) settings are set to get an IP address automatically (meaning DHCP client is enabled for the WAN side of the router).

If still not working, go to "Status" in the router options and hit DHCP "Renew" button.

Also make sure your laptop is getting an IP address from the DHCP server.
Khandakar Ashfaqur RahmanExpert/Consultant

What's the LAN IP of modem?
1.You have already DHCP server.Reserve MOdem's LAN IP into DHCP.heck that you can ping modems LAN IP from DHCP server(vice-versa).
2. Connect your laptop into switch and be sure that laptop is receiving IP from DHCP server.Use "ipconfig /release" and "ipconfig /renew" for troubleshooting.


The modem I am referring to is a modem router and the other device is a switch.

I tried power cycling the modem and switch but can't remember which DHCP setting I was trying at the time on the modem.

There is no WAN port on the switch. It is a unmanaged 16 port switch.

For this to work, you must also be sure that the router's Internet (or WAN) settings are set to get an IP address automatically (meaning DHCP client is enabled for the WAN side of the router).
Does this mean the modem should be set as the DHCP server?

The LAN IP of the modem is

Unfortunately I cannot access the server which is the DHCP so cannot reserve the IP. They do not know the log in password for their server. Is there a way around the password if need be?

Do I need to set the modem's IP to 10.22.22.###?
CompTIA Network+

Prepare for the CompTIA Network+ exam by learning how to troubleshoot, configure, and manage both wired and wireless networks.

Khandakar Ashfaqur RahmanExpert/Consultant

Yes, set modem LAN IP between 100-200 and see what happens.Be sure that other computers are not using using the same IP perhaps it'll conflict.

Or set the LAN IP 254.


So the modem's IP can be outside the DHCP range set on the server?

Sorry, I originally didn't get the part about it being a combo modem/router, so scratch my whole comment. Here it goes again:

If the DHCP server gives out IP addresses in the range of 10.22.22.x, then:

-connect your laptop to the modem and release / renew ip on the laptop
-go to on a browser on the laptop to access the modem's config page
-set the modem's LAN IP to
-release / renew IP again on the laptop
-go to
-set DHCP on the modem to disabled
-unplug the laptop from the modem
-go to your DHCP server and open DHCP
-change DHCP server settings to output as the Default Gateway for clients
-also check the DNS servers to make sure they are valid and working
-connect your DHCP server and your laptop to the switch (don't connect the modem yet).
-on the laptop, go to CMD and release / renew ip address again
-if you get an good ip address for the laptop, go to the next step, if not, post back.
-plug in the modem to the switch
-run ipconfig /all on the laptop and make sure you are getting as default gateway.
-ping and if you get response ping google.com
-if you get response, start surfing the web.
Khandakar Ashfaqur RahmanExpert/Consultant


Please note that he mentioned before he doesn't have access into DHCP server.


Yes, try both.It only depends on Subnet Mask.If it is in the same subnet it can ping each other.Better, you check by connecting your laptop into switch.If it receives IP from your DHCP server find out gateway IP.Configure that IP for your modem's LAN

If the modem is in the 192.168.1.x range and the DHCP range is 10.22.22.x, then their subnets are probably and respectively, which means you're gonna have to change the subnet of the modem, hence the need to make modifications in DHCP. If this is correct and the subnets are different, you'll have to get the DHCP server administrator to make the changes I mentioned previously.


If the modem subnet is different from the DHCP subnet, could I just change the modem subnet to the same subnet as the DHCP?

You mean keeping the same IP? I guess you could, but I know some of them cheap-o modem/routers like the 2-wire ones, don't give you that kind of flexibility. They force certain subnets for certain IP ranges. But if it lets you do it, then go ahead, try it.

It was not the issue with between 192.168.x.x and 10.22.22.x
It was the issue with 10.22.22.x. and it was suggested to use LAN IP between or 254
So, his first 3 octets are fixed here.You shouldn't think about 192.168.1.x


It's very simple issue.You just connect your laptop into switch and check if it gets IP from DHCP server.Then check the gateway IP by ipconfig /all.Configure that IP into modems LAN.

Also be sure that laptop isn't receiving IP from your modem.
> then their subnets are probably and

That's a bad assumption. Unless they specify otherwise, it's usually safer to presume they're all using /24 (
Using a 10.x.x.x address does NOT mean they're using a /8 subnet, at all.

In my opinion, the asker should do an
ipconfig /all
on any computer that has received an IP address from the 2008 Server and see what Gateway address is being assigned.

If it's an IP address that doesn't currently exist on the LAN, make the LAN IP address on the modem/router the same as the Gateway IP address.

If the Gateway address is either or another currently existing LAN IP, then you need to consult with the administrator and find out to what IP address the proxy server, software router/firewall or hardware firewall is sending the outbound traffic after processing and/or NAT'ing it, and set the modem/router's LAN IP to that address.

Did you disable DHCP on the modem/router? Can't have 2 DHCP servers.

Darr247 is correct that modem address must match gateway address from file server.


After connecting my laptop to the switch, the DHCP server assigned my laptop an IP address and ipconfig command confirmed what the gateway was.

I then set the IP of the modem (gateway) to the gateway IP obtained. I also disable DHCP server setting on the modem.

The network and Internet connection now works through the switch and wireless modem.

Thank you.

Do more with

Expert Office
Submit tech questions to Ask the Experts™ at any time to receive solutions, advice, and new ideas from leading industry professionals.

Start 7-Day Free Trial