If you want Net-SNMP to output the numeric OID instead of the textual name do the following

snmpwalk -O n -v 2c -c community server.domain.com .1

The output option n tells snmpwalk to use numeric OIDs. If you want snmpwalk to output the full OID you use the f output parameter

snmpwalk -O f -v 2c -c community server.domain.com .1