Protocols of the TCPIP Suite Part 1
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>> Let's take a look at some of these protocols that
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are a part of the TCP/IP suite.
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The first one we'll take a look at is
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FTP, File Transfer Protocol.
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This is for uploading and downloading files.
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A few things mentioned,
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first there's a reference to the port numbers,
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port 20 and 21.
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We have to know those.
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I also mentioned a specific fact about FTP.
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It's not secure. Credentials traverse
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the network in plain text.
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So that's always going to be
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a problem when you think about network security.
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We don't ever want passwords
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on the network in plain sight.
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We really need to focus on securing the FTP,
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which is coming up on the slide.
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One of the tools that we can use to
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secure FTP is a protocol called SSH.
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SSH is Secure Shell.
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Secure Shell is going to provide us
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security over an unsecured network.
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Secure Shell uses TCP port 22,
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and this was designed to replace some of
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the remote administration protocols,
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like Telnet and FTP,
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or if you work with Unix,
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their utility is called the R utilities.
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All of those have traditionally sent
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passwords across the network in plain text.
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By using SSH instead of plain FTP,
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you get a more secure connection.
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If you're replacing FTP with secure FTP,
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then that now uses port 22,
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also because SSH is really
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the protocol that's providing
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the transport and the security.
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I will also mention that another protocol SCP,
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Secure Copy Protocol,
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uses SSH also port 22.
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They love to ask questions about
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this on the exam because it's
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not just SSH that uses port 22,
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it's SCP and S/FTP,
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which can be something that's tricky to remember.
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Make sure you know these.
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Just spoke about Telnet and said
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that Telnet is also another one of
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those protocols that transmits
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data across the wire and plain text.
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We don't like that.
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Telnet instead of telnetting into a system, we SSH.
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Telnet uses TCP port 23.
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SMTP, Simple Mail Transfer Protocol.
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You have several different mail protocols.
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What SMTP is for is sending
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mail from mail server to mail server.
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When you're talking about sending
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mail from your system up
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or from side-to-side, that's SMTP.
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We've got other protocols that download
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our mail for us or allow us to view our mail,
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but when we're talking about sending, SMTP.
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A friend of mine says to think of it
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as send mail to people,
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and that's exactly right.
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SMTP though really stands for
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Simple Mail Transfer Protocol, port 25.
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Another protocol that we can look at
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is really a protocol and a service.
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It's called TACACS Plus.
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TACACS Plus is port 49,
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and this is a remote authentication server.
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When clients are trying to access
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your network from a remote location,
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maybe they're connecting in a VPN,
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a wireless access point,
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even the back in the day when we used to dial up,
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there needed to be a system
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where we could centralize control,
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and that system was TACACS Plus.
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We'll talk about that more with
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remote access in just a bit.
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An important service on the network.
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DNS, Domain Name Service,
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or you could hear Domain Naming Service.
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You and I like user-friendly names.
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However, for systems to connect,
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they need IP addresses.
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We have to have some reference point
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that we can go to and say,
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"Hey, what's the IP address for weather.com?"
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Or whatever it is we're looking for.
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That's our DNS server.
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Our DNS server provides us with
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name resolutions that we can
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connect to via IP address to host.
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DNS works at port 53.
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Now in a little bit,
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we'll talk about the DNS database and how it works.
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But for now, remote naming to
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IP addresses, to IP addresses,
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to user-friendly names, to IP addresses,
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that's DNS port 53.
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DHCP, another important network service.
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DHCP provides IP addresses to clients automatically.
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Rather than having an administrator
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walk around from host to host,
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IP not and an assigned IP address,
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a client comes online,
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pairs the DHCP server and gets an IP address.
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That's very helpful.
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One of the things we'll talk about is how
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DHCP works and the process called DORA,
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Discover Offer Requests Acknowledge.
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That's coming up in just a bit.
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DHCP operates on port 67 and 68.
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Now an alternative to FTP,
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we talked about this one a little bit earlier
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when we were at Layer 4 of the OSI model.
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We talked about an alternative to FTP called TFTP,
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Trivial File Transfer Protocol.
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TFTP is used in some environments when we're
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looking to download operating systems for devices.
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For example, if I'm doing an operating
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system upgrade on a router or something,
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I might use TFTP.
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A lot of the times we think to use FTP or other means.
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This is port 69, and if you'll remember,
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the difference of TFP,
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it piggybacks on UDP, which is connectionless.
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FTP piggybacks on TCP,
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which is connection oriented.
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Lots of letters in this class.
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[LAUGHTER] I hope you're keeping up.
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HTTP, I think we're all
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familiar with web traffic, Hypertext Transfer Protocol.
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This is port 80.
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If we're communicating with web traffic,
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we're using port 80.
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I'll mention that HTTP is not secure and in of itself.
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We're going to have to add some security in just a bit.
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For now, HTTP is port 80.
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POP, Post Office Protocol.
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I mentioned to you that SMTP was for sending mail.
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When you're downloading email to your devices,
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you're feeling those devices,
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perhaps even on the server.
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What we're looking at is using
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>> one of the two protocols.
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>> POP is very common and we're on Version 3, POP3.
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There's also a protocol called IMAP,
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which will come up in just a minute,
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but that's Internet Mail Application Protocol.
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That would be an alternative to POP3.
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POP3 uses port 110.
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Network Time Protocol.
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Network Time Protocol is really important because it
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controls the synchronization of devices on the network.
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Many network services,
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particularly Kerberos and several others,
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require that our systems be in sync.
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Network Time Protocol is
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a service running on your domain controller that
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helps ensure everybody's using
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the same time clock and that we're synchronized.
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NTP uses port 1,
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2, 3. You know what?
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I was going to tell you guys an NTP joke,
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but my time is always off.
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[LAUGHTER] I hope you enjoyed that.
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I'll be here all week, folks.
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There's our friend IMAP that we talked about earlier.
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An alternative to POP.
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Downloads mail from the server and uses port 143.
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SNMP, Simple Network Management Protocol,
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this is a protocol that
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allows us to capture information on our networks,
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that way we can monitor and be aware of
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the traffic and the various events that are going on.
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With SNMP, we have three main elements, an agent,
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a central manager, and an MIB,
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which is our management information base.
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Our agent is whatever
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network devices are running the SNMP software.
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The central manager, which is ultimately
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your management system that's
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pulling all the information together,
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and then our management information base.
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All your agents contain
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an information database specific to
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the various parameters and
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the information that's being captured.
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This is the database that's used to request
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the agent for specific information and
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then make sure that information is transmitting
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it and formatting in such a way that can be useful.
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That's the management information database.
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A Simple Network Management Protocol uses port 161.
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