[TriLUG] Questions on dyndns.org

[Jason Tower]

it's a little trickier when you're behind a nat device since the ddns 
client cannot simply read the ethernet interface directly to see if the 
IP address has changed.  one approach is to employ a nat device with 
built-in ddns support (some inexpensive netgear routers have it, as do 
smoothwall and ipcop).

the other method is to roll your own if you're handy with that sort of 
thing.  you can easily find your nat public address (which is what you 
care about) by browsing to checkip.dyndns.org, if you can write a little 
script to hit that periodically, parse the IP address, compare it to the 
previous value, and send an update if it is different, you can achieve 
the same results.  odds are someone has already done this before, a 
google search will probably turn up some results.

and of course, after all this you have to set up port forwarding on the 
nat device to point unsolicited inbound traffic to the private IP 
address of your choice.  almost all nat devices support this in some 
fashion.

jason

Vestal, Roy L. wrote:
> All the questions around using dyndns.org's services intrigues me. My
> question is, with their service, or another like it, can you host from
> behind a masquerading firewall? Did I miss something when I read their site?