Whats the deal with SNMPv1, v2 and v3

Here are some of the questions I got from someone few days ago. See my answers inline.

Q: The WLS SNMP agent supports 2 trap versions: V1, V2 and V3. What's the difference between these 3 versions?

[A] SNMPv1 and SNMPv2 are the two version of SNMP implementation. Until WLS 9.x only SNMPv1 and SNMPv2 are supported. Now we have SNMPv3 implemented in WLS 10. Both SNMPv1 and SNMPv2 use community strings to authenticate the packets as SNMP uses UDP (a broadcast protocol). The community string is sent in plain-text in every single SNMPv1 or SNMPv2 packet and the agent uses it to decide to process the packet or discard it. The main difference between SNMPv1 and SNMPv2 is that SNMPv2 added a few more packet types like the GETBULK PDU which enable you to request a large number of GET or GETNEXT in one packet.

SNMPv3 was designed to address the weak V1/V2 security. SNMPv3 is based on SNMPv2 (same packet types), but the main difference is that it is a lot more secure. It does not use community strings but users with passwords and SNMPv3 packets can be authenticated. For more info about SNMP Security from our edocs Security for SNMP.


Q: The SNMP architecture diagram demonstrates that you can poll MBean attribute values from Managed Servers. However, the SNMP commands such as SNMPWALK and SNMPGET don't allow you to specify the addresses and/or names of the Managed Servers that you'd like to poll. How can I tell which Managed Server(s) to poll?


[A] SNMP architecture until WLS 9.x doesn’t allow you to create multiple agents in a WLS domain. The agent implementation was only available in the administration server of the domain. The managed servers will be communicated by the agent when a SNMP manager talks to the SNMP agent running on the administration server. So if you want to get MBean attribute value from a managed server in a domain you must differentiate it using the OID. So you will still point your SNMPWALK and SNMPGET to the admin host and agent port. If you are not sure about the complete OIDs of the managed objects on the WebLogic managed servers you can use snmpwalk to get the root OID of the managed object (or) the attribute by suffixing the managed server's name to the community prefix.