Hi there,

We have a Siemens HiPath wireless controller which is configured to bridge to our LAN on which the server resides. This is used by various wireless laptops.

We can log on to the server, (although this is rather slow) however if you try to copy a large file, say 2mb from a mapped drive back to your client the drive mapping drops and you loose all IP communication with the server.

If i set up a constant ping from my client to the server, as soon as the drive mapping dissapears my ping dies. It takes around 15-20 mins for the ping to start getting a resoponse, and the server to start communicating with the client again. The server only stops responding to that particular client. I know the packets are getting from the client to the server, and as i've wiresharked the port to the server.

If i connect the same machine to the wired LAN there are no issues at all. Its as if some sort of security feature kicks in on the server. There has got to be something in the TCP stream upsetting the server.

The way the Siemens wireles operates (like Cisco and most others) is that packets are sent to a central controller and packaged up for delivery to the access points, which then un-package the data and send it out to the appropriate client/SSID etc. Because an ethernet from the client is ultimatley being stuffed inside another ethernet packet for transport from AP to controller this will affect the MTU. There has got to be something in the TCP stream that the server is unhappy with.

I've had the following settings on the server checked:
set tcp path mtu black hole detection and recovery=off
set always allow ip fragmentation=off
set use specified mtu =off
set maximum interface mtu=576
set tcp defend land attacks=on

The ironic thing is, we have these wireless controllers at another site with an apparently identical server configuration and 100% identical LAN setup, and no issues at all with communicating with the server. If i take the same laptop as used above to that site, everything works fine proving that it's not a client issue.

While i pick through the wireshark grabs to find what's going wrong, does anyone have any ideas on what could be causing the server to drop IP traffic to a particular client.

Many thanks for your help,

Mark Lamond