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Re: Get the external IP address from a Linux box




On Thu, 24 May 2018 07:22:56 +0100 André Rodier said:

> I am looking for a native package on Debian, that can give me the
> external IP address of the machine.
> 
> So far, I used internet sites, but I am sure there is a package that do
> that properly, especially if one site is unreachable.
> 
> Something I can run from the command line, and that would return the
> external IP address.

Unless you have a dedicated IP address, then even if you directly connect to
your ISP (no routers, no NAT) you will likely get a local pool address and from
there routed to the internet by your ISP. In that case your link will have 2
*local* addresses (e.g. 192.168.. or 10...) : one for your side, one for ISP
side. You first enter ISP's local IP pool, and from there exit to the internet
over a real address from ISP's address block.

It can be visualized as a local cloud of ISP. One side of the cloud faces
customers (local reserved IP range), the other side faces the internet (real IP
address pool). E.g. I am connected through 3G modem and my IP and my address
starts with 10.x.x.x - an A class reserved block address.

The only reliable way (AFAIK) is going through some sort of "loop-back"
mechanism to see your external address. External sites are one way of achieving
this.

John Conover's (dig) and likcoras' (script) solutions look promising in that
regard.

Regards
-- 
Abdullah Ramazanoğlu