Hi Victor, it´s working!
I tried your command and i added v3 :
C:\NetXMS\bin>nxsnmpwalk.exe -v3 -u riusnmp -a SHA1 -A Sardina131 192.168.7.254
.1.3.6.1.2.1.1
.1.3.6.1.2.1.1.1.0 [STRING]: Alcatel-Lucent OS10K *** Service Release, January 16, 2013.
.1.3.6.1.2.1.1.2.0 [OBJECT IDENTIFIER]: .1.3.6.1.4.1.6486.801.1.1.2.1.9.1.1
.1.3.6.1.2.1.1.3.0 [TIMETICKS]: 1027116800
.1.3.6.1.2.1.1.4.0 [STRING]: Alcatel-Lucent, http://alcatel-lucent.com/wps/portal/enterprise
.1.3.6.1.2.1.1.5.0 [STRING]: ALU
.1.3.6.1.2.1.1.6.0 [STRING]: Unknown
.1.3.6.1.2.1.1.7.0 [INTEGER]: 78
The problem as you mentioned, i have got a DES encription enabled on NetXMS!!
Now the core it´s working on NetXms , i´ll take a look .
Thanks for your work!