Thanks for your detailed explanation Chris.
Based on the logs that I have, it appears that at some points the
phone uses address assigned to it by my router and sometimes it seems
to use it's internal rmnet0 ip address belonging to 28.* address
segment.

I did different Google searches after reading your post and found that
other people that use VirginMobile complain about even mifi devices
using 28.* address segment internally and sometimes externally instead
of the one from Sprint.

I'll do more testing and see if I can see something that I missed.


On Aug 31, 8:58 am, Chris Stratton <[email protected]> wrote:
> On Wednesday, August 31, 2011 7:48:09 AM UTC-4, ed24 wrote:
>
> > Thaks for your reply.
> > Of course I googled. I know all of the info you put in your reply, but
> > I am still not understanding why there are two WAN IP addresses on the
> > phone itself.
> > It makes no sense to me that a phone uses DOD (Department of Defense)
> > IP address segment of  28.197.54.* for rmnet0 interface.
>
> Think for a minute about a PC on a home network connected to a cable
> modem/router.   The PC has some address - 192.168.x.x or 10.x.x.x on the
> local LAN downstream from that cable modem, and only visible to other local
> machines.  If you visit a get my ip type site with the PC, you'll be told an
> external IP address assigned by the cable company, which may change from
> time to time.  The reason there are two different addresses is that your
> cable modem and/or router are doing Network Address Translation (NAT).  As
> IPV4 space is exhausted, the cable company may even be doing an additional
> level of this on its own.
>
> Now on the mobile network, you have much the same situation, only you have
> NAT (and actually a whole lot more) occurring at the tower or more likely
> the backend network feeding it.  This results in there being an address for
> the rmnet0 interface, which is private to the mobile company's network, and
> also a different external address which comes up when you visit external
> sites like an IP checker page.
>
> Why the private internal address appears to be one reserved to another
> organization and not one such as 192.168.x.x or 10.x.x.x  is unclear, but
> unless you are trying to access a site in the "miss-appropriated" network it
> should not matter, since nothing will get out of the mobile carrier's
> network until it has been address translated.
>
> Likely your ip spoofing alert from your wifi router came about as a result
> of your android device not taking and using a local IP address assigned by
> the dhcp server on your wifi router, but instead picking its own.  This
> suggests there's something wrong with the configuration of your device or of
> the dhcp server on your router.

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