We're having issues where SNMPv3 ceases to accept SNMP requests on our Juniper EX series switches. In what seems like random occurrences, Juniper nodes refuse SNMP authentication credentials.
This is what we end up getting:
rj@MHN00525SYS01:~$ snmpwalk -v 3 -a SHA -A "PASS" -l authPriv -x AES -X "PASS"
-u "username" mhn00416an01 iso.3.6.1.2.1.1.1.0
snmpwalk: Unknown user name
rj@MHN00525SYS01:~$
Our devices were working, but then just stop. The usernames are correct and loaded into the system.
rj@MHN00416AN01# run show snmp v3 users
Engine ID: 80 00 0a 4c 04 31 33 <...snip...>
User Auth/Priv Storage Status
username sha/aes128 nonvolatile active
After dealing with this for some time, we finally decided to investigate. I'm seeing this entry before the system stops accepting requests:
Nov 6 09:44:32 MHN00416AN01 mgd[7996]: UI_COMMIT: User 'rj' requested 'commit'
operation (comment: none)
Nov 6 09:44:35 MHN00416AN01 snmpd[1260]: LIBJSNMP_NS_LOG_ERR: ERR: snmpd: send_trap: USM
unknown security name (no such user exists) (plaintext scopedPDU header type 00: s/b 30)
Nov 6 09:44:35 MHN00416AN01 snmpd[1260]: SNMPD_ENGINE_ID_CHANGED: Warning: Local
engine ID has changed. Passwords for all the users under [edit snmp v3 usm local-engine]
need to be reconfigured.
I have found that simply re-inputting the username/passwords restore access to the device.
rj@MHN00416AN01# set snmp v3 usm local-engine user username
authentication-sha authentication-password PASS
{master:0}[edit]
rj@MHN00416AN01# set snmp v3 usm local-engine user username
privacy-aes128 privacy-password PASS
After a commit
operation, we can access it again.
rj@MHN00525SYS01:~$ snmpwalk -v 3 -a SHA -A "PASS" -l authPriv -x AES -X "PASS"
-u "username" mhn00416an01 iso.3.6.1.2.1.1.1.0
iso.3.6.1.2.1.1.1.0 = STRING: "Juniper Networks, Inc. ex3300-48p Ethernet Switch, kernel
JUNOS 12.3R3.4, Build date: 2013-06-14 02:21:01 UTC Copyright (c) 1996-2013 Juniper
Networks, Inc."
rj@MHN00525SYS01:~$
This issue is happening across a ton of different devices. Models include EX2200-c, EX3300, EX4200 and EX4550 on version 12.3.
Why is this happening and how can I make it stop?