On Sun, Dec 28, 2008 at 12:09:45PM +0000, Tony Arnold wrote: > 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.
Yeah, what he said (wish I'd read this before I'd replied to the previous! :P)
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