I think Im nt expressing myself correctly.
CAM = Content Addressable Memory. So the CAM table is the table the switch uses to relate a physical address (MAC) to the related physical port (eth0, eth1, eth2, wlan in case of..) and so making the communication faster/safer (otherwise it would be a hub). So the router gets a packet with Target-IP, it looks for its MAC in ARP table (if it doesnt find it makes an ARP broadcast asking for such MAC address related to the Target-IP, who answers with his own MAC in an unicast back to router), then it relates this MAC to the CAM table to know wich port such MAC its attached to.
If the CAM table relate a MAC to the wrong port of the switch because of some missmatch (not refreshing when roaming, so not changing from eth1 [port where B router is connected and so, the Tablet while connected to B wirelessly comunicate with A thru eth1] to Awlan), it will send the packets with destination to this MAC to the wrong physical port in the switch, being lost in the arrive to B router (where tablet is not already).
Thats the reason I think A is not letting me connect to it after being in B (but connects fine when not being in B before).
The A-CAM table doesnt refresh its port address from B (eth1) to A (wlan), and so the packet response such as ARP/DHCP are sent into the wrong wire, making the Tablet stay out of network untill the CAM table refreshes (its normal recycle time I read to be 300s, wich makes sense to the time Im waiting for network access after roaming back to A).
Wireless roaming in LAN-to-LAN dual/triple router setup is very usual, I guess CAM tables MUST be dynamic, otherwise they wouldnt accept the change in the port addresses, and would keep sending packets to the old wire making the complete roaming impossible.
So, this is a problem not allowing me to roam, and Im trying to know how much I can do to solve if possible, and why its happenning (normal procedure in my own router, wich would be sick, or any kind of conflict making it not refresh properly while it should be doing).
As you can see, I doubt theres any firmware bug related to Wifi being involved, because I can connect to A perfectly If I dont roam from B before doing it. Anyways, I tried making them both only G before (tried disabling all security access also) I discarded the same SSID setup to track down the failure.