I would have thought that, given a specific OID, an snmpget or snmpset would suffice. However given a specified example from Cisco, it seems that snmpwalk is required. Check out this CCO url and look near the mid to bottom of the page, specifically at steps #3 and #4. i've gone through this procedure, and it seems as though the router won't respond to a snmpget using the show OID. rather, it only responds to a walk.

thanks! -c