Dynamic DNS behind an ADSL router

Dynamic DNS behind an ADSL router

Post by Visvanath Ratnaweer » Sat, 03 Aug 2002 04:03:37



Hi NG

I played around a bit with providing www, ssh, ... from
behind my ADSL router, a ZyYEL Prestige. The machine is
running Linux (SuSE 7.3 professional, kernel upgraded
to 2.4.18). It works but a few questions remain still:

Forwarding the ports 80 and 22 I got www, ssh going.
a) Since ssh works, does it imply that sftp and scp should
work? (I have no clients outside.)
b) Is it possible, or advisable to run an anonymous ftp
using the same technique?

To publish my IP through a dynamic DNS provider I tried
ZoneEdit.com first. Their updating method in ingenious:
you send your userid/passwd through the same router and
their server "sees" the IP. But they didn't give me a
choice in a fixed domain like myname.zoneedit.com
(at least I didn't find any).

At the next stop, DynDNS.org, it was possible to get
myname.dyndns.org but to update the DNS I have to send
the IP explicitly. Furthermore they don't like it if
one "updates" the record regularly even if there are
no changes.

Now the question: What is the elegent way of monitoring
the ISP-given IP address of the router and, if changed,
sending the new IP to DynDNS?

I'm also interested to know your experience with the
various free dynamic DNS providers.

Your feedback appreciated.

Visvanath.
---

 
 
 

Dynamic DNS behind an ADSL router

Post by David Efflan » Sat, 03 Aug 2002 11:53:46



> Hi NG

> I played around a bit with providing www, ssh, ... from
> behind my ADSL router, a ZyYEL Prestige. The machine is
> running Linux (SuSE 7.3 professional, kernel upgraded
> to 2.4.18). It works but a few questions remain still:

> Forwarding the ports 80 and 22 I got www, ssh going.
> a) Since ssh works, does it imply that sftp and scp should
> work? (I have no clients outside.)

Yes.  If your ISP does not have shell accounts, you could get a Unix shell
account elsewhere to test things like that.  One (NetBSD on Alpha boxes)  
is http://www.veryComputer.com/://www.freeshell.org/ although, to
ssh out you would need to become an arpa member (one time $36-50
donation).  Any registered user can ssh in.

Quote:> b) Is it possible, or advisable to run an anonymous ftp
> using the same technique?

Probably adviseable to prevent uploads unless closely monitored.  Most
servers prevent downloading uploads until you (hopefully check them out
and) move them to a different location, but someone can still *your
system or drive by dumping on you.

Quote:> Now the question: What is the elegent way of monitoring
> the ISP-given IP address of the router and, if changed,
> sending the new IP to DynDNS?

I hacked the firmware for my DLink DI-704 so it displays its WAN IP on its
login page without having to login.  Then I periodically (every 5 minutes)
check that using Perl LWP module and run my dynamic DNS update client if
it changes.  The client for my dynamic DNS could run as a daemon and
tickle their server occasionally to grab my connecting IP, but I figure,
why generate internet traffic if I do not have to.

Quote:> I'm also interested to know your experience with the
> various free dynamic DNS providers.

I have had good luck with no-ip.com.  They have a Linux client (binary
source) and do not care if you update them more often than necessary.  
DNS cache expire time is 60 seconds so it propegates within a minute after
they are notified of changes.  Seems to work fine for sshd, smtp and www.  
Examples of my scripts are at http://www.veryComputer.com/
http://www.veryComputer.com/

--
David Efflandt - All spam ignored  http://www.veryComputer.com/
http://www.veryComputer.com/;http://www.veryComputer.com/
http://www.veryComputer.com/;http://www.veryComputer.com/~cgi-wiz/

 
 
 

Dynamic DNS behind an ADSL router

Post by Visvanath Ratnaweer » Sun, 04 Aug 2002 04:05:56


Hi David

Thanks a lot for the information!


> ...

>>b) Is it possible, or advisable to run an anonymous ftp
>>using the same technique?

> Probably adviseable to prevent uploads unless closely monitored.  Most
> servers prevent downloading uploads until you (hopefully check them out
> and) move them to a different location, but someone can still *your
> system or drive by dumping on you.

I meant download only!

Quote:>>Now the question: What is the elegent way of monitoring
>>the ISP-given IP address of the router and, if changed,
>>sending the new IP to DynDNS?

> I hacked the firmware for my DLink DI-704 so it displays its WAN IP on its
> login page without having to login.  Then I periodically (every 5 minutes)
> check that using Perl LWP module and run my dynamic DNS update client if
> it changes.  The client for my dynamic DNS could run as a daemon and
> tickle their server occasionally to grab my connecting IP, but I figure,
> why generate internet traffic if I do not have to.

Hacking firmware doesn't sound trivial ;) In any case it
is a Linksys WAP11 on this side.

I was thinking of gettinge help from a third machine from
outside. A host in the LAN sends a request with username,
password and domain to this third machine. It catches them,
adds the sender's IP-address and send the final request (wget?)
to the dynamic dns provider.

Quote:> I have had good luck with no-ip.com.  They have a Linux client (binary
> source) and do not care if you update them more often than necessary.  
> DNS cache expire time is 60 seconds so it propegates within a minute after
> they are notified of changes.  Seems to work fine for sshd, smtp and www.  
> Examples of my scripts are at http://www.veryComputer.com/
> http://www.veryComputer.com/

Sounds good! I'll check them.

Visvanath.

 
 
 

Dynamic DNS behind an ADSL router

Post by Angela Kahealan » Sun, 04 Aug 2002 17:34:39


I've had no problems with Tzolkin:
<URL:http://www.tzo.com/cgi-bin/afref.pl?affiliate=KAHEALANI.COM>
and they offer a variety of client software methods for updating
your IP address automatically when your computer boots up.
--
Copyright 2002 Angela Kahealani. All Rights Reserved Without
Prejudice, UCC 1-207. All information and transactions are
private between the parties and are non negotiable. http://www.kahealani.com/
 
 
 

Dynamic DNS behind an ADSL router

Post by Visvanath Ratnaweer » Sun, 04 Aug 2002 18:27:23


Hi NG

Quote:>>> Now the question: What is the elegent way of monitoring
>>> the ISP-given IP address of the router and, if changed,
>>> sending the new IP to DynDNS?

> I was thinking of getting help from a third machine from
> outside. A host in the LAN sends a request with username,
> password and domain to this third machine. It catches them,
> adds the sender's IP-address and send the final request (wget?)
> to the dynamic dns provider.

Help from a third server may not be necessary after all.
During manual updates in DynDNS.org I've noticed that the
update form recognizes the sender's IP address. So the
request need to send userid, password and domain only.

The remaining question is "when" to update. The provider
(me too) doesn't like regular updates, even if the address
hasn't changed. David's firmware hacking doesn't apply
because I have ZyXEL. Any suggestions?

Visvanath.
---

 
 
 

Dynamic DNS behind an ADSL router

Post by Alexander Grümme » Sun, 04 Aug 2002 22:25:08


Try www.no-ip.com

They have a client that run under Linux und atomatical get the IP even
when you use NAT.
The Client can run in deaman mode so you only need to start it on boot!

So long Alexander

Visvanath Ratnaweera schrieb:

Quote:> Hi NG

> I played around a bit with providing www, ssh, ... from
> behind my ADSL router, a ZyYEL Prestige. The machine is
> running Linux (SuSE 7.3 professional, kernel upgraded
> to 2.4.18). It works but a few questions remain still:

> Forwarding the ports 80 and 22 I got www, ssh going.
> a) Since ssh works, does it imply that sftp and scp should
> work? (I have no clients outside.)
> b) Is it possible, or advisable to run an anonymous ftp
> using the same technique?

> To publish my IP through a dynamic DNS provider I tried
> ZoneEdit.com first. Their updating method in ingenious:
> you send your userid/passwd through the same router and
> their server "sees" the IP. But they didn't give me a
> choice in a fixed domain like myname.zoneedit.com
> (at least I didn't find any).

> At the next stop, DynDNS.org, it was possible to get
> myname.dyndns.org but to update the DNS I have to send
> the IP explicitly. Furthermore they don't like it if
> one "updates" the record regularly even if there are
> no changes.

> Now the question: What is the elegent way of monitoring
> the ISP-given IP address of the router and, if changed,
> sending the new IP to DynDNS?

> I'm also interested to know your experience with the
> various free dynamic DNS providers.

> Your feedback appreciated.

> Visvanath.
> ---

 
 
 

Dynamic DNS behind an ADSL router

Post by Visvanath Ratnaweer » Mon, 05 Aug 2002 21:08:29


Hi


> Try www.no-ip.com

> They have a client that run under Linux und atomatical get the IP even
> when you use NAT.
> The Client can run in deaman mode so you only need to start it on boot!

David too mentioned no-ip.com. As I wrote in a different mail in the
same thread the question is still *when* to update. I prefer to do
that only if the IP address has changed.

I got the update system of no-ip. Will check how it is done.

Thanks!

Visvanath.
---

 
 
 

Dynamic DNS behind an ADSL router

Post by Peter » Mon, 05 Aug 2002 22:03:57


Quote:>At the next stop, DynDNS.org, it was possible to get
>myname.dyndns.org but to update the DNS I have to send
>the IP explicitly. Furthermore they don't like it if
>one "updates" the record regularly even if there are
>no changes.

So don't update your information if you don't have to.

Quote:>Now the question: What is the elegent way of monitoring
>the ISP-given IP address of the router and, if changed,
>sending the new IP to DynDNS?

You run a client script every 5 minutes (using cron) that checks your
current (actual) IP address and compares it to the last update you
sent to DynDNS.  If they are the same don't do anything, if they are
different then send an update.

I do all this on an OpenBSD system with a Python client script called
ipcheck

Peter M.

 
 
 

Dynamic DNS behind an ADSL router

Post by Thomas Lohmülle » Mon, 05 Aug 2002 23:01:24


I use dyndns.org. There are a few clients who can handle all, what you
need. (http://clients.dyndns.org/unix.php?service=dyndns)

I use dyndnsupdate. You can run syndnsupdate every minute if you wish.
It get's the external IP even behind a NAT-router and updates the
dyndns--account only if neccesary.


> Hi NG

> I played around a bit with providing www, ssh, ... from
> behind my ADSL router, a ZyYEL Prestige. The machine is
> running Linux (SuSE 7.3 professional, kernel upgraded
> to 2.4.18). It works but a few questions remain still:

> Forwarding the ports 80 and 22 I got www, ssh going.
> a) Since ssh works, does it imply that sftp and scp should
> work? (I have no clients outside.)
> b) Is it possible, or advisable to run an anonymous ftp
> using the same technique?

> To publish my IP through a dynamic DNS provider I tried
> ZoneEdit.com first. Their updating method in ingenious:
> you send your userid/passwd through the same router and
> their server "sees" the IP. But they didn't give me a
> choice in a fixed domain like myname.zoneedit.com
> (at least I didn't find any).

> At the next stop, DynDNS.org, it was possible to get
> myname.dyndns.org but to update the DNS I have to send
> the IP explicitly. Furthermore they don't like it if
> one "updates" the record regularly even if there are
> no changes.

> Now the question: What is the elegent way of monitoring
> the ISP-given IP address of the router and, if changed,
> sending the new IP to DynDNS?

> I'm also interested to know your experience with the
> various free dynamic DNS providers.

> Your feedback appreciated.

> Visvanath.
> ---

 
 
 

Dynamic DNS behind an ADSL router

Post by TZO Suppo » Wed, 07 Aug 2002 00:11:26


You should also take a peek at TZO.com, we have many different perl
and other various scripts for many different operating systems and
have excellent support and some great tutorials on the site.

you can get more info on the TZO dynamic DNS at http://www.tzo.com


> I use dyndns.org. There are a few clients who can handle all, what you
> need. (http://clients.dyndns.org/unix.php?service=dyndns)

> I use dyndnsupdate. You can run syndnsupdate every minute if you wish.
> It get's the external IP even behind a NAT-router and updates the
> dyndns--account only if neccesary.


> > Hi NG

> > I played around a bit with providing www, ssh, ... from
> > behind my ADSL router, a ZyYEL Prestige. The machine is
> > running Linux (SuSE 7.3 professional, kernel upgraded
> > to 2.4.18). It works but a few questions remain still:

> > Forwarding the ports 80 and 22 I got www, ssh going.
> > a) Since ssh works, does it imply that sftp and scp should
> > work? (I have no clients outside.)
> > b) Is it possible, or advisable to run an anonymous ftp
> > using the same technique?

> > To publish my IP through a dynamic DNS provider I tried
> > ZoneEdit.com first. Their updating method in ingenious:
> > you send your userid/passwd through the same router and
> > their server "sees" the IP. But they didn't give me a
> > choice in a fixed domain like myname.zoneedit.com
> > (at least I didn't find any).

> > At the next stop, DynDNS.org, it was possible to get
> > myname.dyndns.org but to update the DNS I have to send
> > the IP explicitly. Furthermore they don't like it if
> > one "updates" the record regularly even if there are
> > no changes.

> > Now the question: What is the elegent way of monitoring
> > the ISP-given IP address of the router and, if changed,
> > sending the new IP to DynDNS?

> > I'm also interested to know your experience with the
> > various free dynamic DNS providers.

> > Your feedback appreciated.

> > Visvanath.
> > ---

 
 
 

Dynamic DNS behind an ADSL router

Post by Visvanath Ratnaweer » Wed, 07 Aug 2002 05:04:34



> I use dyndns.org. There are a few clients who can handle all, what you
> need. (http://clients.dyndns.org/unix.php?service=dyndns)

> I use dyndnsupdate. You can run syndnsupdate every minute if you wish.
> It get's the external IP even behind a NAT-router and updates the
> dyndns--account only if neccesary.

Exactly what I was looking for! Thanks a lot!!

Visvanath.

 
 
 

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