376 CHAPTER 16: NETWORK MANAGEMENTThe SNMP default communities include Write (private) and Read (public).User-based SecurityModel (USM)The USM of SNMPv3 provides greater security than pre-SNMPv3configurations. USM includes the following security features:■ Verifies that each received SNMP message has not been modifiedduring its transmission through the network.■ Verifies the identity of the user on whose behalf a received SNMPmessage claims to have been generated.■ Detects received SNMP messages, which request or containmanagement information, whose time of generation was not recent.■ When necessary, protects the contents of each received SNMPmessage from disclosure.USM provides three levels of security on a per-user basis:■ No authentication and no privacy (no encryption of data)This option is comparable to SNMPv1 and does not provide theadditional benefits of SNMPv3.■ Authentication provided by Message Digest 5 (MD5) or Secure HashAlgorithm (SHA) with no encryption of data■ Authentication with encryption of data by Data Encryption Standard(DES)To set an SNMP user’s level of security:1 Login to the NBX NetSet utility using the administrator login ID andpassword.2 Click Network Management > SNMP Settings.3 Click a user name.4 From the Authentication Protocol drop-down list, select the level ofsecurity.5 Click Apply.View-based AccessControl Model(SNMPv1, SNMPv2cand SNMPv3)The View-based Access Control Model (VACM) determines the accessrights of a group that users belong to. You can configure each group tohave access to a view of the MIB, so that users belonging to that group
