Is there any problems with the router that warrants thinking of a FW upgrade?
It's recommended that if the router is working for you then FW upgrade should not be applied.
If you are on A1 or the first generation router, V1.13 is the latest.
for Reb B, v2.05 is the latest and this version(s) should not be applied to the Rev A router. I presume the FW will advise you of this should you try to attempt to apply it to the A1 router.