Last week we were for 5 days on holidays on Sylt. In addition to the mandatory holiday pictures I had fun trying to get connected to the wireless network in the hotel.
The hotel had an unencrypted wireless network for its guests called Gastenetz. Unfortunately it only worked in the lobby and our room was a bit too far away. With iwlist wlan0 scan I was sometimes able to see the network, but I never managed to connect to it. There were three other unencrypted wireless networks available in our room (I do not know where they belonged to) but although I was able to connect to them, they seemed to have no connection to any other network.
At one time I was connected to one of the other networks (thanks to NetworkManager) and all of sudden my jabber client was online. After doing some research I found out that one of the other networks (Haus10) was using the same channel (11) as the hotel’s network Gastenetz and if I hardcoded the ARP entry of the gateway with arp -s 192.168.2.254 00:1x:4x:8x:6x:f4 to the hardware address of the hotel’s router it worked all time. It seems that the access point close to me extended somehow the network to the access point of the hotel I wanted actually connect to.