Connection issues on a laptop

11 Aug 2006 8:00 PM

Gerald Vogt

On my ThinkPad laptop I have a builtin a/b/g WLAN card. I now have a
D-Link WLAN router here to which it will properly connect but most TCP
connections will fail: the computer sends a SYN but never receives an
answer. This is the case with HTTP, IMAPS, POP3S to all servers I have
tested (unlike the usual MTU problems when connections to some servers
will work).

pings will work, though. A ssh with putty to one server on which IMAPS
fails does work also (this was the only TCP connection I have found
working through that wireless card and router). I have tried various MTU
settings for the WLAN interface but it does not make any difference.

When I use a Linksys WPC PC-Card everything works fine (with default
MTU). I have compared all settings in property pages and in the registry
for both interfaces but I cannot find any relevant difference.

The builtin card works fine with other access points and hot spots.

What else could cause these kind of problems?

Thx, Gerald

11 Aug 2006 10:01 PM

Jack (MVP-Networking).

Hi
MTU is a matter of the type of the Internet connection that you are using.
Set it once and it should be OK (
http://www.ezlan.net/Internet_Speed.html ).
Given your description it seems that there is some mismatch between the
Wireless Client, and the Access Point. Try it straight forward with No
Security and NO special settings (like ssh, VPN etc.)
My New Wireless does not work - http://www.ezlan.net/wireless.html
Wireless - Basic Configuration: http://www.ezlan.net/Wireless_Config.html
Wireless Security - http://www.ezlan.net/Wireless_Security.html
Jack (MVP-Networking).

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"Gerald Vogt" <vogt@spamcop.net> wrote in message
news:uY4%23eDYvGHA.1372@TK2MSFTNGP04.phx.gbl...
> On my ThinkPad laptop I have a builtin a/b/g WLAN card. I now have a
> D-Link WLAN router here to which it will properly connect but most TCP
> connections will fail: the computer sends a SYN but never receives an
> answer. This is the case with HTTP, IMAPS, POP3S to all servers I have
> tested (unlike the usual MTU problems when connections to some servers
> will work).
>
> pings will work, though. A ssh with putty to one server on which IMAPS
> fails does work also (this was the only TCP connection I have found
> working through that wireless card and router). I have tried various MTU
> settings for the WLAN interface but it does not make any difference.
>
> When I use a Linksys WPC PC-Card everything works fine (with default MTU).
> I have compared all settings in property pages and in the registry for
> both interfaces but I cannot find any relevant difference.
>
> The builtin card works fine with other access points and hot spots.
>
> What else could cause these kind of problems?
>
> Thx, Gerald

12 Aug 2006 7:06 AM

Gerald Vogt

Jack (MVP-Networking). wrote:

> Given your description it seems that there is some mismatch between the
> Wireless Client, and the Access Point. Try it straight forward with No
> Security and NO special settings (like ssh, VPN etc.)

It is a plain simple open access point with no security setup. There are
no special settings. Both wireless cards use WZC and the network
configurations are identical. There is no firewall nor does the router
have any special settings. Both cards send the same SYN packets with MSS
1460 when trying to establish a TCP connection. The one card receives
the SYN,ACK the other not.

I can ping servers in the internet. I can connect to a SSH server with
putty and I can use a cisco vpn client to tunnel via IPSEC/UDP. putty
does the same kind of TCP connection and succeeds.

Thx, Gerald