I quick check of Knowledge base articles for "P300" finds this one on top.
KBA-5266: Why aren't my P300 bridges connecting.
https://support.ruckuswireless.com/answers/000005266Are your RB and NRBs able to reach the Def-GW or not? Here is text from the article.
I hope this is helpful.
Root Cause
If the NRB is able to reach the GW IP address, or if it establishes an Internet connectivity through the wire, it will shut down the wireless - design of the Mesh mechanism within the P300.
Workaround
Once the GW address is removed from the NRB, the NRB sets a wireless connection across to the RB.
Resolution
A couple of options for solutions:
1). leave the GW address in the NRB blank.
or
2). SSH into the NRB P300 and perform the following command:
rkscli: set eth eth0 disable
The idea here is that the NRB looks for the Gateway through the wire and through the wireless
and if it finds the GW through the wire and through the wireless a loop can be created and thus
it shuts down the wireless.
It is also recommended to place the RB where the POP resides (closes to the internet).