Pb snmp

$ snmpwalk -a MD5 -A 'password' -l authNoPriv -u nagios 10.12.51.122 .1
iso.3.6.1.2.1.4.22.1.4.2.10.12.51.1 = INTEGER: 3
iso.3.6.1.2.1.4.23.0 = Counter32: 0
security service 3 error parsing ScopedPDU
security service 3 error parsing ScopedPDU
security service 3 error parsing ScopedPDU
Timeout: No Response from 10.12.51.122
$ snmpwalk -a MD5 -A 'password' -l authNoPriv -u nagios 10.12.51.122 .1.3.6.1.2.1.4.23
iso.3.6.1.2.1.4.23.0 = Counter32: 0
security service 3 error parsing ScopedPDU
security service 3 error parsing ScopedPDU
security service 3 error parsing ScopedPDU
security service 3 error parsing ScopedPDU
security service 3 error parsing ScopedPDU
security service 3 error parsing ScopedPDU