Sean, Sean Miller wrote:
One of us is a bit confused! > I think we have two completely different things here. > > One is the concept of DNS propogation, but the other is what DynDNS > does which is forward traffic to a given IP. DynDNS does not forward anyu traffic. It just provides a DNS services, i.e., it translates names into IP addresses. > There is no need for low TTL etc. in the forwarding scenario... the > nameservers do not change... they are still DynDNS. By doing that > they can instantly change what IP address the site is hosted on, > because it completely bypasses the whole DNS thing and goes straight > to the server. The nameservers (which have to propogate) are > DynDNS's, but once in place they'll stay there regardless of TTL or > whatever else. If I ask for the IP address of a name, my machine will ask my local DNS server. If that does not know the answer the request gets passed on eventually to DynDNS name servers which will respond with the IP address. My local DNS server will then cache that so the next time I ask, it can provide the answer directly. It will continue to do that until the TTL period expires at which point it will go back to DynDNS again. So if the TTL was set to 24 hours (quite common) and I get an IP address which then changes for that name after a few hours, I'll get the old address and not the new one as that is what is cached in my local DNS server tables. Hence the need for DynDNS to have a very short TTL to reduce the impact of other DNS servers caching the answer. Regards, Tony. -- Tony Arnold, Tel: +44 (0) 161 275 6093 Head of IT Security, Fax: +44 (0) 870 136 1004 University of Manchester, Mob: +44 (0) 773 330 0039 Manchester M13 9PL. Email: tony.arn...@manchester.ac.uk -- ubuntu-uk@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-uk https://wiki.ubuntu.com/UKTeam/
