NMIS supports using SNMPv3 for securing the collection of sensivite network information.  This is especially important from core switches and routers which if compromised could have a considerable business impact.

Configuring Cisco IOS for SNMPv3

The first step is to enable SNMPv3 on your router or switch.  If using Cisco IOS, the commands are below, if using other Cisco operating systems or other vendors, the concepts are the same and the commands will likely be similar.  The most important thing is that the device will support SNMPv3, it will require encryption features if you want to use full auth/priv mode.

snmp-server view NMIS8RO iso included
snmp-server user nmis8 NMIS8 v3 auth md5 nmis4242 priv des nmis4242 

Configuring NMIS8 for SNMPv3