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Connecting Stuff- Pt. 3b

Connecting something that works on a LAN to the internet (WAN)
DDNS, etc.

Material on this page © TK Boyd July 2017... but if you want to translate the page, or circulate it on DVD or intranet, I will allow that with some conditions.

This is one page of many in a sequenced series that try to get you connecting things to LANs and the internet with as few tears of frustration as possible. There is an overview page, which is your table of contents to this material.

This page, and the pages in my "Connecting Stuff" series has not yet had extensive editing. I apologize for the crudeness at this stage, but, unless you need "bells and whistles", and "slickness", I think you can find useful information here.

This is part of a set of SEQUENCED pages. It assumes you have mastered the material in earlier pages.

This page is long and hard.

Be sure you've covered what's in the earlier pages. Until those bits are working, you won't be able to tell if what you're trying to do with the things here are working.

We're going to continue with the EXAMPLE of an IP camera, but, as before, that's just a convenient concrete example. We won't be looking much at camera details.

So far, we have a LAN with an IP cam connected to it. A simple connection-by-cable is fine. I've you've gone further, connected the camera to the LAN via WiFi, it matters not to any of the issues here... but it does add one more Thing To Go Wrong.

The camera should be connected to the LAN by a static (local) internet protocol address... "LIPA". I will say "" in what happens, but EVERY TIME YOU SEE THAT you need to "convert it" to whatever LIPA is "right" for YOUR set up.

I haven't talked about "ports" yet. And don't intend to on this page. I expect your cam is connecting via port 80, but it isn't an issue... yet... as long as your IP cam is connecting to a PC, tablet, smartphone also connected to the LAN SOMEHOW. (If it isn't, go back to the earlier pages where what you need to get that far is discussed.)

All of these things should have been Got Working during earlier pages in this series of pages.

Now we are moving on. We're going to make it possible to "see" the image provided by the IP cam on a device attached to any part of the internet.

This is not, alas, trivial. But it isn't rocket science, either. I managed it!

In many ways, the internet is like your LAN... only bigger. MUCH bigger. It is sometimes called the Wide Area Network, or WAN.

On a LAN, it is not hard to know the LIPA of a device. We don't often NEED to know the LIPA, in day to day use of our LAN, but we could know, if we wanted to. (Devices assigned a LIPA by the DHCP server are a bit of a pain, as they don't always have the same LIPA... but we could know their current LIPA if we wished to.)

If you have file or printer sharing set up for your LAN, then, IN ADDITION to the LIPA system for identifying a resource, there are other, more human-friendly systems. But the LIPAs are there, anyway.

I said that the WAN was "just" a big LAN, so I hope you won't be surprised to learn that the devices connected it have internet protocol addresses. On a LAN, devices have Local area network Internet Protocol Addresses (LIPAs, I call them.) On the WAN, devices have "WIPAs" ("Wide area network Internet Protocol Addresses... a name I've made up, use in my pages, haven't seen others use.)

WIPAs look like the LIPAs I hope you grasped in an earlier discussion... although they can consist of SIX numbers, separated by dots, in some circumstances. (LIPAs are always four such numbers.)

WIPAs will NOT start 192.168.... That range of IP addresses was set aside for use inside LANs.

Cast your mind back just a little way to where I said " devices connected to the WAN have internet protocol addresses". I need to fine tune that a little bit, and you need to think back to things I said about what your switch/ router/ modem is.

The fine tuning: "Devices DIRECTLY connected to the WAN have internet protocol addresses". In any domestic situation I have ever seen, and in many, many small (or medium!) sized business, the computers we use are **not** DIRECTLY connected to the WAN. They, through the LAN, connect to the "LAN side" of a switch/ router/ modem.

IT IS THE "WAN" "SIDE" of the switch/ router/ modem that is DIRECTLY connected to the WAN. And, as such, it will have a WIPA. But, though you can find out what it is (at the moment), it will change from time to time in most people's circumstances, entirely beyond their control.

When you use a computer on your LAN... lets say it is at *L*IPA to search with Google for "hotel London", the request for search results goes from your computer across the LAN to the switch/ router/ modem. From there it goes out across the WAN to Google. Let's say that, for the moment, your switch/ router/ modem is on

Google assembles a page of "answers", and sends that back to, the WAN side of your switch/ router/ modem. And inside your switch/ router/ modem, the message is passed across to the LAN, and sent out to

Whew! All very clever. Isn't it nice that it all Just Happens? "Under the hood/bonnet".

But wait a minute... and yes, this DOES all have to do with how to connect an IP cam for viewing via the WAN....

WHERE did the request for search results go?

I left a bit out, just to get the big picture in place.

You entered a search request for Google.com.

Google actually has many computers serving up answers, but we can ignore how the workload is shared for the moment, and pretend they all come from one place, one "address" on the WAN, one computer, "at" one WIPA.

But we didn't enter a WIPA, did we? We just said "Send this enquiry to Google.com"

The missing bit of magic is the DNS system.

The DNS system is the internet's "telephone directory".

We ask for something to go to Google.com. "The system" takes that and "translates" it into whatever WIPA will get our request to where it needs to go.

Some things.... really BIG things... beyond the reach of mere mortals.... have STATIC WIPAs. (You can buy one, if you REALLY want to, and are rich!)

It's all very like the business you've already studied... static LIPAs and LIPAs assigned by your LAN's DHCP server. Only for the WAN.

There's one thing that you should be able to think of which is always at a static WIPA....

.. can you guess??

Sure?... "Final answer?...

v v v

Yes! The DNS servers... the devices that translate things like "google.com" into a WIPA... they HAVE to be at static WIPAs. (There are many. Your request can "go in" with any one of them. If the one you start at doesn't have the entry your request needs, it will be passed on in a very organized way, until it reaches a DNS server which DOES have the WIPA needed.

Your switch/ router/ modem will have a "setting" in it that tells it the WIPA, where to go, for DNS service. (Or it may be set to get a DNS WIPA from your internet service provider when it (the switch/ router/ modem) connects to the internet though the people you pay for that.)

That's DNS! You "got" all of that, are now an expert, right? Well... maybe not, but read on for a bit. Then come back, re-read from quite a way further up the page, in hopes that things will fall into place for you.


Your switch/ router/ modem "connects" to the WAN by different WIPAs from time to time.

You can't tell people "go to" to connect to my IP cam through my switch/ router/ modem.

By the time you'd got word of your WIPA (today) around to people who might want it, it would have changed again.

Anyway... who wants to deal with numeric IP addresses anyway??

(We'll be back to WIPAs in a moment... but first...)

Which brings me to domain names. "Google.com" is a domain name. YouTube.com, bbc.co.uk, msf.org are all domain names.

The internet is a bit of a "wild west", but at least there are systems in place to make sure (until Bad People subvert the system!) that if you put bbc.co.uk into your browser, you will go where you expect... not to Bob's Barbie Cue supplies website.

And you pay. If you pay, you get control of your domain name. And no one else gets to use it. I happen to own the rights to sheepdogguides.com.

Quite separately from owning those rights, I ALSO pay someone... the same someone, as it happens, though it doesn't have to be thus, to "host" my web pages for me.

I don't know (geographically) where the text on your screen came from!!

It's a bit like the author of an old fashioned, ink on paper book. He has an arrangement with a publisher. He sends text to the publisher. The publisher gets it turned into ink-on-paper. And the books into the shops. The author doesn't know where the book was printed!

I don't know where the computer holding the text your are reading is! I don't know its WIPA. I don't take care of having the WIPA for that web-connected device stored in the internet's DNS system. The people I pay (1and1.com.... very satisfactory, for many years. And 1and1.co.uk, by the way) take care of All That for me.

But they can't take care of my IP cam for me.

So here's how I connect THAT to the WAN....

I use a DDNS service. Yes... two D's. DYNAMIC Domain Name Server service. (I happen to use http://dyn.com/dns/)

"DDNS" is an unfortunate name. It isn't the NAME of my domain that is dynamic (i.e. changing.) It is where to find my domain, i.e. its WIPA.

To use DDNS, you need to register (pay for) ANOTHER domain name. (Well, "another" if you also have web pages published by means of a web hosting service, like my SheepdogGuides.com)

Often you can arrange that through the same people who do your DDNS for you.

In my case, there's http://mon7nc.dyndns.org

Here comes something really clever:

Somewhere on the LAN where my IP cam is (or, more usually these days, within the switch/ router/ modem that connects that LAN to the WAN), there's a bit of software that from time to time checks: "What WIPA is this switch/ router/ modem/ system using AT THE MOMENT to connect to the WAN?"

If it is the same WIPA as it was using previously, all is well, the system just goes to sleep again for a little while.

If the WIPA has changed, the system sends a message off to the Nice People who manage my DDNS for me. THEIR computer then passes the word on to the "bigger" DNS system that my switch/ router/ modem is no longer at the old WIPA, and what the new WIPA for my system is.

So! Except briefly, from time to time, (and in practice it isn't an issue), if you ask the DNS system for the WIPA to get to the switch/ router/ modem connected to the LAN with my IP cam on it, using mon7nc.dyndns.org gets you the right WIPA!

((NEW CHAPTER)) === So! We can bring the world to our door!


We're prepared... you need to be careful here, by the way!... to let the world see what our IP cam sees. (You'll probably make some setting inside the IP cam to "allow anonymous viewing", or some such. But that's one of the "camera details" that aren't core to this essay.)

But the IP cam isn't the only thing on the LAN. You certainly don't want to let "the world" into anything on the LAN!

So now, the next step...

Network Address Translation....

Inside your switch/ router/ modem, there's a way... and again, I can't explain in detail, as each device uses different menus, etc... there's a way to "forward" stuff. It is often under the heading of "services", or "NAT" (network address translation). You DON'T want to go down the "DMZ" or "VPN" routes, by the way, tempting though they may seem from "stuff" the menus in your switch/ router/ modem might seem.)

In essence, you "tell" your switch/ router/ modem "If someone comes asking for http service, send them to device zzz", where "zzz" is the LIPA of the IP cam.

You may... more on this in a later essay... be asked to say what "port" this will involve. For now, say "port 80", or "standard http port". ("http" NOT "the whole of the internet")

Get the above right... (and yes, I think this essay needs massaging...) and now anyone anywhere can see the image your IP cam displays! (And remember that "IP cam" was just an example of "a thing" that you can put on your LAN that can be connected to. The camera is an "answers only" device, a "just output TO the internet" devices. There are other things, which use ALL of the above, but go even further. You can, for instance (for about $30) add a "thing" on your LAN which allows someone out on the internet to turn an LED connected to the thing connected to your LAN on or off . And if you can turn an LED on or off, you can do.... LOTS.

BACKTRACKING a little....

So... you're trying to get all that working. And it doesn't.

It won't "do" for every day, but you CAN find out your (current) WIPA.

Let's say that in my case my WIPA (for the moment) was And that I THOUGHT I'd set up "everything" to allow people to see my IP cam's image with http://mon7nc.dyndns.org.

If I put into my browser, I SHOULD (for the moment) get the same result... but without using the DDNS part of "everything". So, if I do, I've narrowed down where my problems lie.

That, by the way, SHOULD be sending a request OUT, over the internet, even tho/ught the requesting computer and the IP cam, if only they knew(!) are on the same LAN, and could "talk" directly.

If I still don't, I should look up the static LIPA I THINK I have the camera on. Let's say I think it is on, entered into a browser on a computer on the same LAN as IP cam is on SHOULD bring up the image from the cam. If it doesn't there may be NO PROBLEM with ANY of the rest! Don't mess with the rest until the "simple" viewing is working!!

Very often, simple typos are the problem. LIPAs have to be entered, re-entered, and must be entered RIGHT each time. Passwords. Usernames. Etc.

Also: There may be firewall problems. Probably not at the "" level... but they'll raise their ugly heads before too long. But BE CAREFUL! If, in desperation, you (recklessly) turn your firewall off for a moment, "to see if THAT works", be sure to turn it on again quickly.

My anti-malware offers a very useful "verbose" mode, in which it tells me everything that is going on. So if it WERE blocking something I wanted to do, I'd see a message at the time I tried to do it.

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