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When SNMP was defined and published, there was no official way to discover SNMP enabled devices in the network. This might be caused by the well known security issues of SNMP itself, as if you know there is such a device in the network, you can somehow sniff the wire to get community names. (Thus, if you are a device administrator, make sure you hide your devices if they should not be discovered.)

However, some SNMP products, such as SNMP MIB Browsers, might use an unofficial way to detect devices. Our sample, snmpdiscover, implements one common approach.

Simple Device Discovery for v1 and v2c (IPv4)

UDP allows broadcast, so if we broadcast an SNMP GET request with OID 1.3.6.1.2.1.1.1.0 using community name "public", some devices will reply with their device information. In this way we know both the device IP address and type from the replies.

Note that you should avoid using "public" as community name, as it is so well known.

Discovery for v3 (IPv4)

RFC 3414 defines a discovery process for SNMP v3. This gives us a chance to discover all v3 enabled devices in the same network by broadcasting a simple discovery request without any credentials.

As in this way the device IP address is revealed, make sure your devices don't use a common user name and passwords.

Last edited Jan 27, 2016 at 12:59 PM by lextm, version 3