Index: /branches/rel_apv_10_7/usr/click/webui/htdocs/new/src/apv/models/admintools/snmp/__init__.py
===================================================================
--- /branches/rel_apv_10_7/usr/click/webui/htdocs/new/src/apv/models/admintools/snmp/__init__.py	(revision 39903)
+++ /branches/rel_apv_10_7/usr/click/webui/htdocs/new/src/apv/models/admintools/snmp/__init__.py	(working copy)
@@ -360,6 +360,12 @@
                 host_cli = 'snmp host %(ip_str)s %(version_id)s "%(community)s"' % data
             else:
                 # version 3
+                # check username exist
+                user_manager = SNMPV3User.get_manager(self._session)
+                try:
+                    user_manager.get({'username': instance.username})
+                except Exception:
+                    return cli_parse("invalid username", BlankParser(nonblank_exception=CLICmdError, nonblank_msg=__('%s does not exist in user database of SNMP.') % instance.username))
                 host_cli = 'snmp host %(ip_str)s 3 "%(username)s"' % data
             cli.cmd(host_cli,
                 BlankParser(nonblank_exception=CLICmdError, supplement=True, ignore_msg=[