Now we're going to move on and talk about managing devices with SNMP.
In this module,
we are going to get an in-depth discussion of the protocol much
more in depth than we did in the previous module.
We're going to talk about the OID, the object identifier,
look at the format and look at some of the data that it will return to us,
and we'll also look at the management information base,
or the MIB files.
We'll take a brief look at the format of the MIB files
just to completely round this out.
Hopefully, you'll never be writing MIB files, but you never know.
Some of you might be a lot more adventurous that I've ever been.
When you have a network management system polling a device using SNMP
polling like we discussed in the previous module,
SNMP polling uses UDP, which is the connectionless IP protocol.
Now a lot of people find it kind of counterintuitive that a network
management protocol uses a connectionless transport,
but when you sit and think about it,
you'll recall that TCP has to have that three-way handshake,
and you've got to do acknowledgements for each packet sent and received,
and there's a lot more overhead with the TCP
protocol than there is with the UDP.
UDP just kind of puts it on the wire, and if it gets there,
great, and if not, then it gets dropped.
It's specifically used in streaming video and streaming audio
for like voiceover IP and video conferencing,
but when you're doing SNMP polling,
you don't necessarily need all of the overhead that TCP brings to
the table because all of that overhead might not be a problem if
you're polling 5 or 10 or 15 devices,
but if you're doing SNMP polling for a few hundred devices,
you can very quickly bog down your management
server with all of the TCP traffic.
With the UDP packets, the source port is any port,
usually it's random, it's one of the high random ports.
The destination is 161.
Now you can encrypt SNMP using TLS or datagram TLS,
TLS or DTLS, and in that case, the destination port is 10161.
Now in this course,
we won't be talking about TLS or DTLS anymore in depth than this simply
because that gets more into the encryption side of network management and
we're just looking at the SNMP protocol itself,
which we will implement towards the end of the course.
For SNMP notifications, also known as SNMP traps in SNMP version 1,
it also uses UDP for all the same reasons we talked about on the last
slide and the source port from the managing device is 162 and the
destination port is usually any random high port. And just like with SNMP polling, you can use TLS or DTLS and it uses port 10162.