[Asterisk-Users] Re: Granstream BT100 - only partial success

[Tom Ivar Helbekkmo]

"Stephen R. Besch" <sbesch at acsu.buffalo.edu> writes:

> 3) Don't know if it will make a difference, but I always set the
> router field to 0.0.0.0.  There is no such thing as a valid router
> IP on a private network - they are not routable by design.

That's not actually correct.  Private networks (also known as RFC1918
networks) work just like any other IP nets.  They can be subnetted,
with internal routing between subnets, and hosts and routers on them
route packets just like on any network, including the use of default
routes.  Very often, the default route on an RFC1918 net leads out to
the actual Internet, through a NAT gateway.

The "not routable" bit is actually just a prohibition against letting
the RFC1918 networks (their routes, and their addresses) be visible on
the Internet.  If connected to the Internet, they must use a gateway
that hides them behind one or more official addresses.  The reason is,
of course, that this lets them be used in many places, saving official
address space.

> I had quite an argument with Grandstream about this when I first
> purchased the phones.  As a result, the firmware was modified to
> accept a null router entry for use with private IP ranges.

I guess that can be useful, anyway -- you can then configure a phone
(whether it's on a private or a "real" net) to not have a default
route, and thus not be able to communicate with anything outside its
local network.  On the other hand, anyone with physical access to the
phone can reprogram it, so it doesn't protect against abuse from the
inside...

-tih
-- 
Tom Ivar Helbekkmo, Senior System Administrator, EUnet Norway Hosting
www.eunet.no  T +47-22092958 M +47-93013940 F +47-22092901 FWD 484145