Hi,
I've set up the ad-hoc network with WPA-Encryption. This is working fine. I can access all nodes if i configure the ra0 (ralink wifi) interface with static ip addresses. I've done this for testing purpose only. Normally only the bat0 interface has an ip address.
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# iwconfig lo no wireless extensions. dummy0 no wireless extensions. usb0 no wireless extensions. eth0 no wireless extensions. ra0 Ralink STA ESSID:"ceR{)|n$v#pp|fJX" Nickname:"RT2870STA" Mode:Ad-Hoc Frequency=2.442 GHz Cell: DE:BB:8C:08:B8:EC Bit Rate=36 Mb/s RTS thr:off Fragment thr:off Encryption key:D83E-521A-8B9F-7C95-3ACE-D477-****-****
the ralink driver misses one very important feature to reliably run a larger adhoc mode cell: Assigning a manually chosen BSSID. Therefore, it would not suprise me if you experienced "cell splits" from time to time. To verify this theory you can watch the BSSID (Cell) field on the involved nodes and run a continuous ping on your statically configured setup. If I am correct you also will experience packet loss and the BSSID will change.
Regards, Marek