DHCP not working reliably through open (unsecured) wireless connection

[Meldrew]

Hi everyone.

 

We have a wireless/DHCP/VLAN issue that we're experiencing and have pretty much run out of ideas and I wondered if anyone had any suggestions. I can't guarantee that we haven't done something stupid though.

 

The setup we have is a managed wireless system (D-Link) with 2 SSIDs. The main one is setup with 802.11x authentication and works fine. The other SSID called 'mobile' is basically for BYOD and is setup as an open unsecured network. This mobile network is setup so that the AP pushes 'mobile' data out on VLAN2 through the network infrastructure. We then have a static VLAN 2 port in our main switch to which we have a small switch (which we call our mobile switch) connected that we have our DHCP server connected and an Internet filtering (censornet) server which is the route out to our ISP.

 

We can assign a static IP address to a device, connect to mobile and browse the Internet perfectly. We can ping the DCHP server fine, no problem at all. If however we choose to get a DHCP address, we only intermittently get an address. Mostly we get a 169 address and on a laptop, limited or no connectivity, ie no DHCP address available.

 

To try to diagnose, we tried connecting a laptop via cable to the 'mobile' switch and it gets a DHCP address fine. We connected an ancient simple AP (DWL-900AP+) with an unsecured open network to the 'mobile' switch and with that we can get a DHCP address perfectly too.

 

This makes it sound to me that the VLAN 2 is the cause of the issue, but we can ping the DHCP server on a static address through this just perfectly and get Internet access just fine.

 

Any thoughts? If my description of the setup needs clarification, let me know and I'll scribble something out and upload...

 

Meldrew

[cpjitservices]

Is the link between the 2 switches marked as trunked or tagged ? You'll need to tag VLAN 2 to that link to be able to pass down the traffic.

[Meldrew]

Is the link between the 2 switches marked as trunked or tagged ? You'll need to tag VLAN 2 to that link to be able to pass down the traffic.

 

The link is trunked, but as we can happily ping and pass other data down the VLAN (again when using a static IP), we assume that the trunking/tagging side of things is correctly setup.