Dynamic Host DNS Registration

Sten Carlsen ccc2716 at vip.cybercity.dk
Tue Jul 12 17:59:38 UTC 2005


Thanks for keeping this on the list, after my holiday I can't post 
anything and I have not had the time to figure out why yet.

In my setup I have one PC running at all times. This PC is running 
Linux, RH9 at the moment, I will change to a recent Fedora Real Soon 
Now, I have everything running on this machine:
Bind
dhcpd
samba (facing inwards only)
postfix (not sendmail, I can figure out how to configure that)
nfs
xinetd with imap4 pop3
ssh

This PC has 2 NICs, one facing inward and one facing outward. I have my 
public address on the outward facing NIC and a 192.168.x.x address on 
the inward facing NIC.

If I connect my laptop on the inside, it will get an address like 
192.168.x.x and the address of the imap4 server is in the same range.
If I connect my laptop say at the airport, it will have some public 
address and it will connect to my imap4 server using the same name 
"mail.x.x" as I use on the inside.

The last building block you may want to look at is views in bind. That 
allows me to have two different IP given out for the same name depending 
on my physical location. For the outside world I have 5 nameservers, for 
the inside world I have only one. Everything is controlled from my bind 
as a stealth server on the outside and just by using my bind on the inside.

I hope this makes sense, we might have to discuss this off list if it 
gets too specific, let's see.

With this setup the only change I see when going out is the services 
missing because I don't regard them as being safe enough to bring 
outside; e.g. telnet and samba and smtp because my ISP has closed port 
25 incoming.


Jim Logan wrote:

> Sten Carlsen wrote:
>
>> Your'e welcome
>>
>> I also have my DHCP-server on the same machine as my DNS-server, 
>> works like a dream.
>>
>> I found one very nice thing about using the exact same names inside 
>> as well as outside: using a laptop, inside or outside, you don't need 
>> to do anything like having different mail-server names or such 
>> things. Only IP numbers change according to which view you use.
>>  
>>
> Does that work through a NAT firewall?  Why are the addresses 
> different?  How does this work?
>
> -Jim
>
>

-- 
Best regards

Sten Carlsen

Let HIM who has an empty INBOX send the first mail.



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