dynamic ip address - how to get to know my ip address?

Hi there,

my ISP provides me with a dynamic ip address. I'm using a wireless LAN
router made by SMC to connect to the internet. I want to get to know the
public ip address from a computer that is located in the local network
behind the router's firewall. But, of course, the router's NAT replaces the
public ip address with the local one.

How do I get to know the public ip address the ISP gave me?

Currently, I'm not using Linux. But I consider to set up a Linux box that
will be accessible from the internet. I guess, this problem is not
platform-dependent. Unfortunately, my router does not have a telnet
interface or any other interface that would provide me with the public ip
address. Only, if login to the web interface manually, I can see the current
status including the current ip address.

Can I solve this problem with standard TCP/IP tools? "ping" does not give
any evidence -- I was sniffing with Ethereal to miss no information.

Do I need help from an external system that can tell me my ip address? Is
there a service, I can use?

Thanks in advance,

Johannes

Johannes Lebek wrote:

> Hi there,
>
> my ISP provides me with a dynamic ip address. I'm using a wireless LAN
> router made by SMC to connect to the internet. I want to get to know
> the public ip address from a computer that is located in the local
> network behind the router's firewall. But, of course, the router's NAT
> replaces the public ip address with the local one.
>
> How do I get to know the public ip address the ISP gave me?
>
> Currently, I'm not using Linux. But I consider to set up a Linux box
> that will be accessible from the internet. I guess, this problem is
> not platform-dependent. Unfortunately, my router does not have a
> telnet interface or any other interface that would provide me with the
> public ip address. Only, if login to the web interface manually, I can
> see the current status including the current ip address.
>
> Can I solve this problem with standard TCP/IP tools? "ping" does not
> give any evidence -- I was sniffing with Ethereal to miss no
> information.
>
> Do I need help from an external system that can tell me my ip address?
> Is there a service, I can use?
>
> Thanks in advance,
>
> Johannes


You did not tell us the model number of the SMc router.

A quick review of the SMC site suggests that SMC routers are basically
standard cable/dsl routers which use web based administration to set up
the firmware.

That is, one would use a web browser to access the ip of the router's
firmware then read the parameters from its configuration pages and to
make any changes needed to accept a new computer or operating system as
part of its network.

In Windows, do you use Internet Explorer or Netscape to access the
router? If so, you can use a browser such as Konqueror or Mozilla or
Opera in linux to do the same thing.

On Sun, 6 Jul 2003 16:16:51 +0200, Johannes Lebek <(E-Mail Removed)> wrote:
> Hi there,
>
> my ISP provides me with a dynamic ip address. I'm using a wireless LAN
> router made by SMC to connect to the internet. I want to get to know the
> public ip address from a computer that is located in the local network
> behind the router's firewall. But, of course, the router's NAT replaces the
> public ip address with the local one.
>
> How do I get to know the public ip address the ISP gave me?

There are various dynamic DNS services (web search for 'dns hosting'). I
use no-ip.com. They have Windows and Unix clients that can run in the
background so they can periodically grab your connecting internet IP.
Although, I hacked my Dlink gateway firmware so I can monitor its
WAN IP from its login page with a Perl LWP script without having to login,
and just update DNS when necessary.

I also have a wireless SMC router, but it has hardware/firmware problems
that make it not worth messing with.

Another option, if you have an internet web host somewhere, is to write
your own CGI that you tickle with wget occasionally and stores your IP in
a file you can access from anywhere. But it is simpler in the long run to
use dynamic DNS (so you can configure clients for a fixed name).

--
David Efflandt - All spam ignored http://www.de-srv.com/
http://www.autox.chicago.il.us/ http://www.berniesfloral.net/
http://cgi-help.virtualave.net/ http://hammer.prohosting.com/~cgi-wiz/

"Johannes Lebek" <(E-Mail Removed)> writes:

>my ISP provides me with a dynamic ip address. I'm using a wireless LAN
>router made by SMC to connect to the internet. I want to get to know the
>public ip address from a computer that is located in the local network
>behind the router's firewall. But, of course, the router's NAT replaces the
>public ip address with the local one.

>How do I get to know the public ip address the ISP gave me?

That's hard.

>Currently, I'm not using Linux. But I consider to set up a Linux box that
>will be accessible from the internet. I guess, this problem is not
>platform-dependent. Unfortunately, my router does not have a telnet
>interface or any other interface that would provide me with the public ip
>address. Only, if login to the web interface manually, I can see the current
>status including the current ip address.

My router allows telnet. I use an expect script to login and
check the IP address. Maybe you can use an expect script and
lynx to login to the web interface.

>Do I need help from an external system that can tell me my ip address? Is
>there a service, I can use?

That's what I did before I came up with the expect script for
telnet. I would "ssh" to a system where I had access, and there run
the command "echo $SSH_CLIENT".

Hi David,
thanks for the answer.
See my comments inline...

> There are various dynamic DNS services (web search for 'dns hosting'). I
> use no-ip.com. They have Windows and Unix clients that can run in the
> background so they can periodically grab your connecting internet IP.

My router has a built-in support for dynamic DNS service TZO. But it is not
a free service. I will not use this service often, so I don't want to spend
25 bucks on it. Actually, I don't want to use any of these services. I just
want to sent a e-mail to my mailbox, each time I dial in.

> Although, I hacked my Dlink gateway firmware so I can monitor its
> WAN IP from its login page with a Perl LWP script without having to login,
> and just update DNS when necessary.

That sounds interesting! If I were able to modify my login page of my
router's web interface, I could place the current ip address on this page.
This is brilliant. But I don't know how to hack my firmware.Sounds risky
somehow...

>
> I also have a wireless SMC router, but it has hardware/firmware problems
> that make it not worth messing with.
>

I had some problems with firmware, too. This seems to be a big problem of
SMC. The model I have is a SMC 2804 WBR. There was a firmware upgrade in the
beginning of June. I installed it because they promised to support WPA.
Unfortunately, after applying this firmware upgrade WEP did not work any
more. It took two weeks until they released a new firmware fix, although
they were aware of the problem one day after the erroneous firmware was
released. (I called them and they already knew.)

> Another option, if you have an internet web host somewhere, is to write
> your own CGI that you tickle with wget occasionally and stores your IP in
> a file you can access from anywhere. But it is simpler in the long run to
> use dynamic DNS (so you can configure clients for a fixed name).
>
> --
> David Efflandt - All spam ignored http://www.de-srv.com/
> http://www.autox.chicago.il.us/ http://www.berniesfloral.net/
> http://cgi-help.virtualave.net/ http://hammer.prohosting.com/~cgi-wiz/

> www.whatismyip.com does this.
>
> You could try a little script which issues "wget
> http://www.whatismyip.com/" and then parses the (simple) resulting
> index.html.
>
> This will work regardless of what device is doing the NAT and whether
> you have any access to it.
>
> Regards, Ian

Ian,

thank you very much for this link. This is what I was looking for!
You saved my day! I appreciate your help.

Johannes

On Sun, 6 Jul 2003 19:00:11 +0200, Johannes Lebek wrote:
>
> I haven't heard of an expect script before. Is this kind of a response file
> (like you can use for automatic installations)? If I know what is is, I will
> give a try. Because this seems to be the easiest way to retrieve the ip
> address without using the internet itself. Thanks, Mister.
>
> If using the internet, asking www.whatismyip.com is easier to use than using
> for a SSH server, I have access to. (By the way, the link to this service
> was given to me as an answer to my posting, too. Thanks, Ian!)
>
> I will look for some information about expect scripts. If you can provide me
> a link to some documentation, I would be very grateful.

try man expect on you linux box.

expect will let you script commands to an interactive session.
It will not navigate a web page unless you can use keyboard keys to
navigate the webpage.

> try man expect on you linux box.
>
> expect will let you script commands to an interactive session.
> It will not navigate a web page unless you can use keyboard keys to
> navigate the webpage.

Does this include the "tab" key? Then it might work!

On Sun, 6 Jul 2003 19:11:58 +0200, Johannes Lebek wrote:
>> try man expect on you linux box.
>>
>> expect will let you script commands to an interactive session.
>> It will not navigate a web page unless you can use keyboard keys to
>> navigate the webpage.
>
> Does this include the "tab" key? Then it might work!
>

using pull down menuse might be kinda tough.

"Bit Twister" <(E-Mail Removed)> schrieb im Newsbeitrag
news:(E-Mail Removed)...
> On Sun, 6 Jul 2003 19:11:58 +0200, Johannes Lebek wrote:
> >> try man expect on you linux box.
> >>
> >> expect will let you script commands to an interactive session.
> >> It will not navigate a web page unless you can use keyboard keys to
> >> navigate the webpage.
> >
> > Does this include the "tab" key? Then it might work!
> >
>
> using pull down menuse might be kinda tough.

Fortunately, it's simple page. No JavaScript and simple input fields only.
But it consists of frames... I guess lynx is not able of handling frames, is
it?