[Techtalk] Setting up an ADSL router for remote access

[David Sumbler]

I have an elderly (i.e. even more elderly that me) friend who lives a
long way off; we keep in touch mostly by using Pidgin for IM.  For many
years I have managed to keep her computer more or less functional,
mainly by my logging in remotely.

Very often the sort of things I need to sort out are merely uncollapsing
folders in Evolution when she finds she can't see her emails.  She
sometimes accidentally changes things like this because her eyesight is
not very good; she has also been diagnosed with Alzheimers, and although
that is at a fairly early stage she is easily confused if I try to
explain how to correct things.

Some months ago she had to get a new router.  She was supplied with a
new one by her ISP (BT).  Unfortunately this means that I can no longer
log in to her computer because the router has not been set up to permit
that.

She is now having computer problems which need to be sorted out.  They
sound like simple things such as the collapsed folders I mentioned, and
also she clearly has not applied any software updates for many months:
she has probably forgotten how to.  So we have decided that she will
send her computer to me to fix, which will probably only take a matter
of minutes.

It occurred to me that if she were to send her router as well I ought to
be able to set that up so that when she reconnects everything I can then
get an SSH connection to her computer.  When her router is here with me
I doubt that I shall be able to get an internet connection with it: it
is set up with her account details and BT is quite likely to refuse a
connection because it is not coming through a BT phone line.  But so far
as I can see I don't need an internet connection: I just need to be able
to log into the router from her (or my) computer and set it up to allow
incoming connections from me to be routed to her computer.

Can anyone see a problem with this?  Is there anything I have overlooked
which might prevent me from setting up the router the way we need
without having an active internet connection?

David