Re: Re[2]: FQDN hostname
On Friday 05 Apr 2002 6:41 am, Alan Poulton wrote:
> Thursday, April 04, 2002, 7:35:53 PM, Richard Cobbe wrote:
> > First question: do you want your FQDN to be
> > hotstuff.bc.hsia.telus.net? With exim, I ran into some problems with
> > that (mail for root@localhost getting sent to my ISP and so forth). I
> > ended up giving my system a hostname that wasn't valid outside my
> > network, home.rcc.
>
> HMM! Interesting point! No, I don't want mail for root@localhost to get
> sent to my ISP. In that case, should I change my hostname? Or is there
> a way to prevent it from routing to my ISP?
>
> My etc/hosts now looks like this:
>
> 127.0.0.1 hotstuff.bc.hsia.telus.net localhost loopback hotstuff
> 192.168.43.1 hotstuff.bc.hsia.telus.net hotstuff
>
> -----
>
> I have a Dynamic IP through my ISP - should I have (or need) the second
> line?
It seems to me it might be useful for you to take a step away from the problem
and realise three things.
1) Its not your computer but each interface that has an IP address
2) Names (including FQDN) are ways of refering to the IP address and are
converted between the two using a DNS (Domain Name Server). Within the
internet system the authority for a name (e.g name.com) and the names with
are further qualified extendsion (eg extension.name.com) are delgated when
you register the domain name
3) E-mail addresses (user@hostname) are related because of MX records in the
dns
I have a linux box acting as a gateway on my home network. The outside world
has a cable modem with a dynamically assigned IP address although I have had
the same one for 6+months. Because of that stability, and because I have
bought the domain name chandlerfamily.org.uk which is managed by domain name
management company (they host the official DNS for chandlerfamily.org.uk) I
am able to set up their DNS to reflect this IP address in the name
home.chandlerfamily.org.uk
The internal side of that gateway box is a LAN which that box has IP address
10.0.10.100 and all my home machines have names in the 10.0.10.xxx space.
The DNS for that address space is hosted by me on the gateway box. Since
NONE of these IP addresses or the names associated with then are to be made
available to the outside world I run a DNS server on the box that allocates
the name roo.home to 10.0.10.100 and names like kanger.home pooh.home etc to
my internal network machines.
So for my gateway box what is its FQDN. I have a choice - I can use either
roo.home OR home.chandlerfamily.org.uk. I have chosen roo.home and thats
what is in /etc/hostname.
I mention e-mail addresses because others have although its a little bit of a
red herring and irrelevent to your original question. As you see below I am
using the chandlerfamily.org.uk address as my address. The DNS server for
chandlerfamily.org.uk (see above) has a MX record that tells it the ip
address of the mail server which will receive mail for my domain. Within the
domain management company that server receives the mail and forwards it to my
ISP under the e-mail address they happen to have given me
(alan.chandler@blueyonder.co.uk). I use fetchmail to receive the mail from
my isp and fetchmail sends it to a local mail server (exim) as though it
should go to alan@fetchmail.home. Exim is configured (separately from the
DNS) to decide how to manage mail. It will send assume any mail with domain
names *.home or chandlerfamily.org.uk as local and will not use DNS MX record
lookup to decide what to do. Instead it delivers to local mailboxs where my
mail program can get at them.
I have configured Exim to recognise addresses of the form
alan-outside@chandlerfamily.org.uk specially (for testing) and not to hold
them local but to forward them to my ISP with the -outside tag removed. My
ISP recieves the mail from me because it comes from an IP address of one of
the boxes on its internal network (it does this check because the domain name
is different to blueyonder.co.uk and it doesn't want to act as a relay for
spammers but it does want to relay e-mail for its customers). It then
forwards it by doing the DNS MX lookup and finding my domain management
companies mail server (which eventually routes it all the way back to me as
described above)
--
Alan Chandler
alan@chandlerfamily.org.uk
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