Hi,
Backfire any version doesnt support some boards like tplink 740N ver 3. I could install trunk version on the same and run it fine but bacfire doesnt run. Here is the ticket link https://dev.openwrt.org/ticket/9807
No problem with trunk but arpnat is only available for kernel 2.6.39 . Hoping someone will port arpnat patch on the newer kernel.
backfire will not support tplink 740 ver 3 as said by ndb and it wont be fixed. So we are left with trunk version and 2.6.39 kernel on which arpnat is not supported. Hopefully it maybe ported to newer kernel