reading external ip

My ISP recently changed my IP. That's ok, they have to deal with their
problems, but I want to protect access to my home network through a script
that polls my router for its ip and then emails to my webmail account any
change in ip.

How do I do that? I've googled as well as I can, but all I get is
unanwered questions!!

Please someone suggest a fruitful query or perhaps even (oh joy!) a really
good link to the issues I'm dealing with.

Please help.

Thanks.

stephen wrote:
> My ISP recently changed my IP. That's ok, they have to deal with their
> problems, but I want to protect access to my home network through a script
> that polls my router for its ip and then emails to my webmail account any
> change in ip.
>
> How do I do that? I've googled as well as I can, but all I get is
> unanwered questions!!
>
> Please someone suggest a fruitful query or perhaps even (oh joy!) a really
> good link to the issues I'm dealing with.
>
> Please help.
>
> Thanks.

It depends on the kind of connection you have. I have PPPoE at home, so
I do what you describe in /etc/ppp/ip-up.local so I can ssh back when
I'm on the road. On my laptop I put a custom script in /sbin/ifup-local
for other reasons (i.e., no mail).

How did I find them? I read the start-up scripts to find what were the
user-defined scripts. Your distro may use different ones.

"stephen" <(E-Mail Removed)> wrote in message
news(E-Mail Removed)

> My ISP recently changed my IP. That's ok, they have to deal with their
> problems, but I want to protect access to my home network through a
> script that polls my router for its ip and then emails to my webmail
> account any change in ip.
>
> How do I do that? I've googled as well as I can, but all I get is
> unanwered questions!!

Write a simple script that is run in a cron job.

If the output of

wget -O- whatismyip.com 2>/dev/null | awk '/Your ip/ {print $4}'

is different from the last time you checked, then send the email. ("Your ip"
is an exact literal text string, _not_ your current IP number.)

tony

--
use hotmail for email replies

stephen wrote:

>
> My ISP recently changed my IP. That's ok, they have to deal with their
> problems, but I want to protect access to my home network through a script
> that polls my router for its ip and then emails to my webmail account any
> change in ip.
>
> How do I do that? I've googled as well as I can, but all I get is
> unanwered questions!!
>
> Please someone suggest a fruitful query or perhaps even (oh joy!) a really
> good link to the issues I'm dealing with.

The exact answer depends on your distro, but generally, the dhcp client will
run a script after address change, which can be used to generate the
e-mail. There are a couple of ways of determining the new address. Also,
you may want to see if your host name changes, when the IP does. If not,
you've got a consistent host name, which will always provide the current
address.

--

(This space intentionally left blank)

stephen wrote:

> My ISP recently changed my IP. That's ok, they have to deal with their
> problems, but I want to protect access to my home network through a script
> that polls my router for its ip

How will this help you "protect" your LAN ?

I'm really curious as to why it would be needed.



--
J

All your bits are belong to us - again.

stephen wrote:
> My ISP recently changed my IP. That's ok, they have to deal with their
> problems, but I want to protect access to my home network through a script
> that polls my router for its ip and then emails to my webmail account any
> change in ip.
>
> How do I do that? I've googled as well as I can, but all I get is
> unanwered questions!!
>
> Please someone suggest a fruitful query or perhaps even (oh joy!) a really
> good link to the issues I'm dealing with.
>
> Please help.
>
> Thanks.
>
>
>
>

I think in the dyndns.org (maybe the spelling is wrong) there are some
scripts to do something like that, but it was a long time ago when I
check it and I can be wrong...


--

Jose Maria Lopez Hernandez
Director Tecnico de bgSEC
(E-Mail Removed)
bgSEC Seguridad y Consultoria de Sistemas Informaticos
http://www.bgsec.com
ESPAÑA

The only people for me are the mad ones -- the ones who are mad to live,
mad to talk, mad to be saved, desirous of everything at the same time,
the ones who never yawn or say a commonplace thing, but burn, burn, burn
like fabulous yellow Roman candles.
-- Jack Kerouac, "On the Road"

> How will this help you "protect" your LAN ?
>
> I'm really curious as to why it would be needed.

Sorry, my bad explanation. I mean 'protect my access' as in maintaining my
ability to connect to my home network from outside. If my ip changes while
I'm away, I have no way of knowing my new ip. I guess I'm looking for a
way for a net node to discover the network's external ip.

The real solution, I guess, is to pay for a static ip, but I figure I'm
paying too much already for my dynamic one.

I'm looking into the ideas others have posted here.

Thanks.

>
> Write a simple script that is run in a cron job.
>
> If the output of
>
> wget -O- whatismyip.com 2>/dev/null | awk '/Your ip/ {print $4}'
>
> is different from the last time you checked, then send the email. ("Your ip"
> is an exact literal text string, _not_ your current IP number.)
>
> tony

I am using a DLink wireless router with a web admin interface. So
using wget I could parse out the ip address? Thank you. I give that a
try, but haven't found out how to pass authentication.

On Fri, 27 Aug 2004 23:26:37 +0200, Jose Maria Lopez Hernandez wrote:

> stephen wrote:
>> My ISP recently changed my IP. That's ok, they have to deal with their
>> problems, but I want to protect access to my home network through a script
>> that polls my router for its ip and then emails to my webmail account any
>> change in ip.
>>
>> How do I do that? I've googled as well as I can, but all I get is
>> unanwered questions!!
>>
>> Please someone suggest a fruitful query or perhaps even (oh joy!) a really
>> good link to the issues I'm dealing with.
>>
>> Please help.
>>
>> Thanks.
>>
>>
>>
>>
>
> I think in the dyndns.org (maybe the spelling is wrong) there are some
> scripts to do something like that, but it was a long time ago when I
> check it and I can be wrong...

Looks like just the thing. Thanks.

stephen wrote:

> My ISP recently changed my IP. That's ok, they have to deal with their
> problems, but I want to protect access to my home network through a script
> that polls my router for its ip and then emails to my webmail account any
> change in ip.
>
> How do I do that? I've googled as well as I can, but all I get is
> unanwered questions!!

no-ip.org is what you need. Sign up for account, you get a small client
that will track ip address of interface you specify and then it will
update your 'whatever.no-ip.org' address.

If you for some reason don't want to do it like this, you could run
script in crontab to check the current ip address of interface and
compare it to previous ip.

Here is a script you could start building on :

#!/bin/sh

ifconfig eth1 | grep "inet addr:" | cut -c 21- | cut --delimiter=" " -f
1 > /tmp/eth1-current-ip
cmp /tmp/eth1-current-ip /tmp/eth1-ip > /dev/null 2>&1
if [ $? -ne 0 ]; then
echo "IP address of eth1 has changed."
cp -f /tmp/eth1-current-ip /tmp/eth1-ip
fi