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Separate Wi-Fi clients from the domain DHCP server allocation?

Posted on 2014-02-11
Last Modified: 2014-02-25
My client (a small college) has a Windows SBS server running dns, dhcp, etc. There are approx. 50 desktops used by college staff and students.

Additionally, students are allowed to connect to the college's Wi-Fi using their iPhones, iPads, etc. in order to browse the internet.

There is a Netgear DSL modem, a Sonicwall Firewall and 5 CISCO wireless access points throughout the building.

Windows SBS DHCP server is configured to allocate IP Addresses from - Everything else is reserved for printers, ip phones and networking equipment above.

The problem I have is that students using Wi-Fi from their phones/tablets, get allocated an IP Address by the DHCP server and soon after the DHCP server runs out of IP addresses to allocate.

These Wi-Fi clients dont need access to the college's network. They only need internet access.

How can I resolve this issue?
Question by:cgruber
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Expert Comment

ID: 39851404
You could
expand the network to allow more IPs in the same range.
so instead of -
you could use -
Giving 510 usable address instead of 253.

You do this by changing the subnetwork to (instead of

or 2.
You could have two subnets.  So you keep 192.168.0.X for what you have today
and then put 192.168.1.X just for wireless.
Both networks would have the subnet
and the router / dhcp would have to be setup to route and assign the addresses.

Expert Comment

ID: 39851405
Does anyone connect through the wireless that would have the need to connect to the college's network?

Is there a controller in play or are these APs standalone devices?  Usually, there is is a setting to allow for guest connections through the APs that would be on their own IP addresses and only have access to the Internet not the internal network.

Other option would be to setup a second IP address subnet with it's own DHCP pool of addresses that could be used just for the wireless network.  This would entail creating a separate VLAN and assigning the ports on the switches that the APs are patched into.  Then when a DHCP request from the wireless came through, it would recognize that it was coming through on the VLAN and assign an appropriate IP address.

What make/model are your switches?  Are they Cisco also?

If they are Cisco, here is some information on configuring VLANs on them:


Accepted Solution

Mandeep Khalsa earned 500 total points
ID: 39851434
To separate your WiFi with your physical network you should use Sonicwall. Configure a port say X4 on the Sonicwall to be part of the WLAN zone and turn on the DHCP Server for that zone. Connect all your Cisco AP's to that port (X4) using a switch. Then update your firewall rules to deny traffic flow from WLAN to LAN.
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Author Comment

ID: 39851444
Yes, some wi-fi clients (such as staff with laptops) will still need access to the college's network.

switches arent cisco.

I dont want to expand the current network to allow more Ips, I want to keep the hotspot users away form the network.

Author Comment

ID: 39851451
KhalsaComputer - That sounds interesting. I will try that on the Sonicwall with just one WAP and see if it works

Expert Comment

by:Mandeep Khalsa
ID: 39851461
Just so you know doing it with the Sonicwall will stop your staff members with laptops from accessing the network unless you put in specific firewall rules.

Author Comment

ID: 39851479
I could simply setup a separate WAP in the staff office which would bypass the Sonicwall and have its own SSID and passcode !?

Expert Comment

by:Mandeep Khalsa
ID: 39851498
Yes a separate WAP that is placed on your LAN will continue to give you the same results that you are achieving currently, the only difference being the SSID and password will be restricted to staff only.

Expert Comment

ID: 39851566
I am not absolutely positive on the Sonicwall, but most WAPs will allow for multiple SSIDs.

You might be able to configure all your Sonicwalls with one SSID for staff and another SSID for guests, which would eliminate having to add additional WAPs

Expert Comment

by:Mandeep Khalsa
ID: 39851693
From my understanding the newer models of Sonicwall are capable of having multiple SSID's however in this case, if we are going to block the whole WLAN zone from accessing the network multiple SSID's will accomplish nothing.

Expert Comment

by:Mandeep Khalsa
ID: 39851748
Just remembered that Sonicwall by default only allows SonicPoints to pass traffic on the WLAN so you will have to do one more step for this to work. Go to Network -> Zone -> WLAN and under wireless tab, uncheck the box for "sonicpoints" only (should be at the bottom).

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