> Does one or more of the SNMP MIBs define some of these counters to
> be only 32 bits?

RFC2233 says it this way

   For interfaces that operate at 20,000,000 (20 million) bits per
   second or less, 32-bit byte and packet counters MUST be used.  For
   interfaces that operate faster than 20,000,000 bits/second, and
   slower than 650,000,000 bits/second, 32-bit packet counters MUST
   be used and 64-bit octet counters MUST be used.  For interfaces
   that operate at 650,000,000 bits/second or faster, 64-bit packet
   counters AND 64-bit octet counters MUST be used.

If you need one-size-fits-all I think I'd bump the byte counters to
64 bits but leave the rest at 32.

Dennis Ferguson