You configure secure usernames under Administration > System Settings: SNMP ACLs. These configuration options are available under Security Names:

Displays the controls to add a security name.

Specifies a name to identify a requester allowed to issue gets and sets (v1 and v2c only). The specified requester can make changes to the view-based access-control model (VACM) security name configuration. This control doesn’t apply to SNMPv3 queries. To restrict v3 USM users from polling a particular subnet, use the RiOS Management ACL feature, located in the Administration > Security: Management ACL page. Traps for v1 and v2c are independent of the security name.

Specifies the password-like community string to control access. Use a combination of uppercase, lowercase, and numerical characters to reduce the chance of unauthorized access to the SteelHead. Community strings don’t allow printable 7-bit ASCII characters, except for white spaces. Also, the community strings can’t begin with a pound sign (#) or a hyphen (-). If you specify a read-only community string (located in the SNMP Basic page under SNMP Server Settings), it takes precedence over this community name and allows users to access the entire MIB tree from any source host. If this isn’t desired, delete the read-only community string. To create multiple SNMP community strings on a SteelHead, leave the default public community string and then create a second read-only community string with a different security name. You can also delete the default public string and create two new SNMP ACLs with unique names.

Specifies the host IPv4 or IPv6 address and mask bits to which you permit access using the security name and community string.

Adds the security name.