Chad wrote: ktx wrote: Chad wrote:
Guess what? TTL isn't always the best thing to rely on. Some DNS servers update 15 days at a time, or even longer.
Wrong-O. Yeah, there are some ISPs that do not obey that TTL (which is no only against the RFC is is pathetic IMO), but I have NEVER heard of a company caching DNS queries for 15 days or longer. Even piss-poor ISPs like AOL don't do more than a week (maybe they've changed that though, to actually obey the RFC I don't know). I can guarantee if you were to set your TTL properties to an acceptable time seeing how much your IP address is changing it would eliminate at least some of the problems users are experiencing. It won't hurt anything, and it certainly may help, so why would you not use it?
Uhm, if you know all this.. whats our TTL? Mr. Wise Guy..
The www RRs in question probably have no specific TTL, they just take the one of the zone, being 86400 aka 1 day. This is positive caching. Negative caching is a zone-wide setting and seems to have a TTL of 10800 aka 3 hours. Ha! All your TTL... ;-)
I do consider it bad practice to advise people to use another DNS server but the ones of their access provider, though. A whole lot of issues come to mind (among them privacy and security, all those queries going out on the big Net, an external dependency for such a crucial network service (freeing you of all the distributedness and redundancy standard DNS burdens you with and giving you a single point of failure in return, even one with many many links that might fail between you and that SPoF...), problems with DNS views...). If DNS TTL already is not "the best thing to rely on" while it has been in use for many many years and is in numerous RFCs and all, I wonder very much about "opendns.COM".
Which of course doesn't mean that some ISPs might not do *TheRightThing* when it comes to DNS. I've seen references to ComCast, but does anyone know why they might break the rules? To the unfortunate customers of such ISPs I'd recommend they switch access provider, or, if they're computer literate enough and can't switch for some reason, I'd recommend to use `dig +trace` for those names that don't seem to resolve properly.
If you do this (use `dig +trace`) for (www.)whatistheamazon.com you'll see that the DNS servers that ought to know about this zone are "ns1.chadohman.name." and "ns2.chadohman.name.". The WHOIS records for that zone also point to those 2 DNS servers. But what I see from and about these DNS servers is veeery strange... (like they seem not to know about themselves...) I suspect there are serious problems at these authoritative DNS servers or the zone they're in.
Can any of the MH people explain why using opendns.COM solves the problem or even what the exact problem is according to you?
BTW, this is what opendns.COM lists as causes for DNS problems:
Why is a domain (URL) not resolving with OpenDNS?
If you're using OpenDNS, and a domain (URL) is not resolving, you should see the OpenDNS search results page. That indicates a possible DNS problem. If you are getting a "Page not found" error message in your browser, that is not a DNS problem. If you are seeing the OpenDNS search results page for a domain you know exists, the likely causes are one of the following:
* The domain's DNS has problems. To date, this has been the most common result of our investigations. If you are the domain owner, please double-check your nameservers.
* The domain was recently moved from one webserver to another, and the TTL (Time To Live) has not expired. Before moving a domain, please lower your TTL to the minimum available, so all nameservers know to check often for updates.
* There is a problem with an OpenDNS server. While we expect this to be the rarest of the three possibilities, we do want to be sure, so please contact us with details so we can investigate.
As I see it, the problem at hand might very well be the first one.
For in the true nature of things, if we rightly consider, every green tree is far more glorious than if it were made of gold and silver.
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