SNMP v3 trap and engineID

When sending an SNMP v3 trap from the sender to the trap receiver, the authoritative engineID is the trap sender's engine ID.   Below is a method to remotely discover the engine ID of  the remote SNMP sender (likely SNMP agent):

use the net-snmp snmpwalk command, and add the command option: "-Dsnmp_sess_open" and do a snmpget v3 with your credentials, and you should get something like this:

snmp_sess_open:   probe found engineID:  80001f888016fb784553d902ac
.1.3.6.1.4.1.3432.8.1.1.7.0 = Gauge32: 0

The agent's engineID is right there: 80001f888016fb784553d902ac

You can also try "-Dlcd_get_enginetime", which gives you local engineID

On the other note, I have written the SNMP trap receiver that can detect the incoming engineID automatically. Check it out at github: https://github.com/tiebingzhang/WapSNMP

On a local Linux machine running snmpd, you can find out its engine ID by:

cat /var/net-snmp/snmpd.conf

If you have any SNMP v3 user configured, you should see one or more lines like this:

usmUser 1 3 0x80001f888016fb784553d902ac 0x68636d2e736e6d70763300 0x......

EngineID is the 4th element: 0x80001f888016fb784553d902ac