Episode: 149
Title: HPR0149: DynamicDNS
Source: https://hub.hackerpublicradio.org/ccdn.php?filename=/eps/hpr0149/hpr0149.mp3
Transcribed: 2025-10-07 12:27:20

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Music
This is Hacker Public Radio. I am Clat 2, topic for today, dynamic DNS. I will never forget
I was at bar camp about this time last year and some guy was sitting around talking about
how in order to increase the safety of his internet usage there at the convention he was going
to SSH to his computer at home and I guess open up a you know like doing X forwarding and
surf the web basically you know bouncing off his computer at home via this essentially SSH
tunnel that he set up to his to his home computer and I thought wow that's kind of cool sounds
pretty neat I wonder how that's done and I asked and you know everyone's really helpful but
sometimes it takes a while for things to sink in depending on who you are and how much about
networking you know about and I don't really know that much about networking so it took me a while
to number one get around to actually sitting down and really investigating this I knew what
SSH was but up until very recently it only really SSHed within my local network so to be
able to be out and about with my triple EPC and then decide to SSH home you know for a
file that I've forgotten or or just to you know check something on my computer whatever I didn't
know how to do that in order to do that you have to use a dynamic DNS service and what is dynamic
DNS service well Thomas Jefferson described dynamic DNS as a method or network service that
provides the capability to a network device using the IP protocol suite so that would be your
computer or a router or whatever to notify a domain name server to change in real time also known
as ad hoc the active DNS configuration of its configured host names or addresses so in plain
English and that was from Wikipedia in plain English it's basically if you're out and you want to
talk to your home computer via the interwebs you need a bridge between you two you can't just you
know type in your local your local area network IP address like 192.168.1.0 or something and expect
to find your home computer obviously so in order to do this I'm just going to go through the
process step by step basically it's it's actually pretty easy there are free services that will do
this for you you just have to set it up so it's the setup that I'm going to go over the places that
you can sign up for accounts are no IP dot com that is in oh dash IP dot com as in you have no
static IP address no dash IP dot com another one that I keep hearing about I have not tried is
dyn DNS dyn DNS dot com I've heard they're really good as well it's just for what I whoever I
asked first talked about no IP so that was the one that I knew about and that was the one that I
tried and kind of just invested the most into so I just I went with them but but both of them as
far as I know have free services if you want super fancy feature feature-rific service packages
you can pay but just their basic simple IP forward or their dynamic dns service is free so go to
one of those two sites maybe go to no IP just because that's what I'm going to be covering no
IP dot com sign up for an account they'll email you they'll make sure you're a real person if
you're not a real person you will you will probably not be able to open an account if you are a
real person you'll respond to the email and then you can go to no IP dot com and log in okay so
once you've logged in you'll actually see the IP address that they're picking up from you on
that computer in the upper left hand corner you can trust that or what I like to do just in case
is I like to go to what is my IP dot org that is what is my IP dot org no it's not it's what's my
IP dot org what's my IP dot org or you can just Google I mean just Google the words what is my IP
address and it'll come up with a billion sites that will basically read your IP address and then
feed it back to you so let's just assume that the IP address that I got shown was 23 dot 23 dot 23
dot 23 okay really easy to remember so what you do is you go to the no IP dot com oh and by the
way I've got graphics for all this stuff so what you can do right now if you're at work or in
front of the computer go to straight edge linux dot com slash interweb that is straight edge linux
dot com slash interweb now it's got basically everything that I'm going to be talking about right
here lots of graphics it's going to be pretty difficult to screw this one up okay first step after
you've gotten your IP address you log into no IP dot com and on the left column there is the
your your domains that you can manage or your DNS that you can manage and you click on the add
button that will give you an add a host window and there you can pick out your host name so that
would be instead of for instance www dot whatever dot com you know it'll be something so let's just
say that I'm going to do a fan site for the sci-fi show lex lex dot and then they give you a drop
down menu of the possible the free domains that you can choose from so they they have set domain
names there's there's a couple of good ones I don't I didn't honestly I don't care because I
just I'm using it for my personal use it's not really I'm not setting up like a web server here
I'm just this is just so that I can go out and SSH back home but let's just say that I wanted
to sound cool and so I take geek galaxy dot com all right that works the host type is just
going to be a DNS host that's all I want is I want them to take my IP address and put a name
in a DNS server somewhere for that IP address simple as that and then down below that you see the
IP address I think auto magically it has the IP address that they've detected that you're you're
on right now so if you're on another computer configuring this for a different computer you want
to enter in the IP address manually but verify that it's right and if it's if it's what IP address you
want to talk to eventually then just go for it you hit save or apply or whatever down at the
bottom and now it has taken the name that you've given it Lex dot geek galaxy dot com and it has
pasted that over you know 23.23.23.23.23 okay so now if you you type in Lex dot get get galaxy dot
com you will go to in theory that IP address 23.23.23.23 now I say in theory because two things one
it takes a couple of minutes for it to kick in and then two your computer needs to be configured so
that it will accept whatever kind of traffic you're going to send it's send it's send to it what kind
of traffic you're going to send to it depends on why you're doing this I am doing it for SSH I just
want to be able to SSH into my box I don't want to do anything else no web servers no email servers
nothing like that I just want to SSH it's neither here nor there the way to do it right so I guess the
simplest way is to go into your Linux machine find your firewall application not all distros will
have a GUI configuration panel for for firewall mine does it's Fedora 9 KDE desktop it's got a
firewall app right there in the administration category so if you're on something you know that
does provide you that there you go if not just go back I think there was like I know that there
was a Linux action show where Chris just talked all about firewall applications I'm sure there
are probably a couple of other podcasts out there that have mentioned firewalls and good ones
to use so you can you can do that you can also do this with IP tables so if you just don't want to
do the GUI thing or you just can't decide which firewall configuration application that you want to
use you know just do it with IP tables but let's assume that you've got a firewall configurator
and so you're going to open that up by default on a Fedora system everything's turned off
so what I did was I just enabled the SSH which is port 22 and the kind of traffic that is
is going to be TCP as opposed to like UDP or something else that some person who knew something
about networking would probably be able to rattle off really quickly so it's port 22 that's SSH
you can enable that you're going to be tempted to enable the WWW protocol the HTTP port 80
because you're going to be like you know I can just set up a little web server and it could be fun
don't do it it's too dangerous people turn your computer into a zombie
yeah I left that one alone because I don't know what I'm doing so SSH good enough for me
but you can do all kinds of cool stuff I mean you can do WWW you can do secure HTTP you know
the zombie open VPN you know just whatever you're going to set up now like I say if you don't know
if you don't have a firewall configuration application just open up a terminal and you're
going to CD into slash Etsy slash sysconfig and in there are is the IP tables document
so then IP tables or nano or whatever text editor you want to use you'll you'll have to be
root for that so SU and then put in your password or pseudo whatever you do open up IP tables
in a text editor and you're going to want to add one line to this it's going to be dash capital A
space all caps input space dash P space TCP space dash in that's in is in I forget what it stands for
in is in marry anyway space TCP space dash dash s port that's s is in fam port space 22
space dash in is in marry the word state space dash dash state space established space dash j
space except easy right okay you might want to put a comment above it just to kind of identify that
as something new that you've added recently you know just so you so you have it there for yourself
so that if you've totally screwed things up or you want to turn this function off you can go back
and turn that off I'm no expert in in IP tables so if there's a better way of doing that someone
can certainly either tell me or leave it in a comment on on on the hacker public radios site
under this this episode I I will even offer to revise this episode if if I've done something really
really awful with that IP table line so there you go that'll that'll open up port 22 is what
that's going to do though it's going to allow it's going to listen on port 22 now if you go to your
web browser and put in Lex dot Geek galaxy dot com suddenly things start to happen well actually in
your web browser nothing will happen but if you go into your terminal and ssh space your user name
on that computer at Lex dot Geek galaxy dot com it will finally ask you for a password and whether
you accept the key and all this other stuff and you should be able to just ssh right in and open up
the terminal or forward the x window server whatever you want to do you're now inside your box
from afar except one thing what if you've got one of them fancy wireless routers on your home
network and so your your router is sort of acting like it's own little firewall
it's probably not going to let port 22 traffic into it and so you're going to have to go into
your router before you before this any of this will work and you're going to have to do some port forwarding
because basically the router I mean it is it's a little firewall in a way because it's sitting
between your computers and the worldwide web out there and it's it knows that the only traffic
that should be coming from outside your house really is you know the worldwide web stuff the port 80
or 80 80 whatever it is so to get to get it to say that port 22 is going to be forwarded to one of
your computers you need to go into your router now if you've never configured your router and again
probably the audience of pack of public radio probably everyone's done that but if you haven't I mean
it's really easy just look on the back of the router the bottom of the router find out what
little IP address it it it it has by default if you haven't changed it already
usually it'll be like either 192.168.0.1.0 or 0.1 or 10.0.0.0.
.1 just kind of depends on the company but it'll be something very very similar to that and you
can change that as long as it's like within 192.168.0.0.0.0.2.5 I guess you'll you'll be fine but
anyway so that's your router go into it you'll probably need to type in a password and a username
and if it's if that username and that password is admin and password now would be a great time to
give it something a little bit more personal and once you're in there it's going to unfortunately
differ for every router it just really really depends on what brand it is I happen at the place
that I'm living right now I've got a net year router doesn't belong to me but it's what I've got
you go into it I found the port forwarding slash port triggering control pane go into that
and the the ones that they gave me were like ftp htp age of empires quake real audio just tell
net bizarre bizarre choices but it was easy to add and add a custom service I just clicked on add
custom service I gave the the service a name but just plain text human readable name for my own
reference ssh start port in port both of them are 22 and then the server ip address would be you
know whatever the ip address of the computer that you actually want to ssh into so I've got that
configured to like let's say 10.0.0.8 that would be the computer that I'm actually
going to on my my internal network now there may be a way to configure that to some kind of
device that will allow you to you know ssh into any one of your computers on your internal network
but I haven't gotten that far yet and I don't really have the need to do that so I'm pretty happy
right now with just being able to ssh into my my main workstation and that's how it's done so
if as long as you're doing that you got your router you've got your little port forwarded from
the router to the physical computer you've got the dns assigned to your real world ip address
you're good to go one more catch is that the reason you're doing all this is because you don't
have a static ip address right if you had a static ip address that never changed
then you wouldn't be doing this you'd be able to go anywhere
and just type in the ip address and you'd be fine
the thing about that is though that it doesn't you know not many of us have the privilege of
having a static ip address and usually the ip address is going to you know it's a dynamic ip
address from our isp now the good news is that I have talked to a lot of different people
and they've all said the same thing and I have found it to be very true is that you're even though
it is technically not a static ip address your your real world ip address just doesn't seem to change
that often like if you go if you just start right now going to what is my what's my ip.org like every
every week just check your ip address I'll bet you anything it'll be the same like practically
every time that's how it's been for me it's been like that for for good two months now it's been
the same exact address I've not not worried about it and it was like that of my previous address as
well I don't I don't think probably in about a year I don't think my ip address changed I don't
I didn't really check it every every month or anything but I I'm pretty sure for a very long time
it did not change so it wasn't really a problem and that that's good because I called my isp at
one point and asked about a static ip address and it was going to be really expensive so just I
wouldn't even worry about it but if you're checking and you're finding that it is changing a lot
then what you might have to do is download and a little application that no ip.com offers and I'm
sure dy and dns offers one as well but I know that no ip.com offers it for Linux as well as other
platforms and you can go you can download this application and it's basically just a little app
that sits and checks what your ip address is your outside ip address is and if it changes then this
application detects that and lets no ip.com know that it has changed and it adjusts accordingly
and again that's just part of the free service so you can just download that and get it started
and you should be good to go that's how you do dynamic dns I hope this has helped some people
have fun and don't don't open up you know yourself to any trouble out there it's
it's a big world wide web so just you know only do what you need to do be secure use you know
good passwords and all that other good stuff don't hesitate to check out the tutorial online again
it's at straightedgelinux.com slash interweb i n t e r w e b lots of screenshots on how to do
everything I've talked about makes it pretty simple so have a good time enjoy bye
thank you for listening to Hack with Public Radio
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