Intermittent incorrect DNS resolution?

RijilV rijilv at riji.lv
Wed Jan 16 22:20:06 UTC 2013


Also client programs don't always honor TTLs either.  For example, JAVA
defaults to ignoring TTLs and holding IPs forever.

*networkaddress.cache.ttl (default: -1)*
Indicates the caching policy for successful name lookups from the name
service. The value is specified as as integer to indicate the number of
seconds to cache the successful lookup. A value of -1 indicates "cache
forever".

Depending on who your clients are, your milage may vary.

.r'


On 16 January 2013 14:13, George Herbert <george.herbert at gmail.com> wrote:

> On Wed, Jan 16, 2013 at 2:00 PM, Erik Levinson
> <erik.levinson at uberflip.com> wrote:
> > Hi everyone,
> >
> > I'm having an unusual DNS problem and would appreciate feedback.
> >
> > For the zones in question, primary DNS is provided by GoDaddy and
> > secondary DNS by DNS Made Easy. Over a week ago we made changes to
> > several A records (including wildcards on two different zones), all
> > already having a TTL no greater than one hour.
> >
> > The new IPs on those A records have taken many millions of requests
> > since the changes. Occasionally, a small amount of traffic appears at
> > the old IPs that those A records had. This is HTTP traffic. Packet
> > captures of this traffic show various Host headers.
> >
> > Attempting to resolve those various Host headers from various networks
> > in Canada against various random private and public resolvers and
> > against the authoritative NSs all yield correct results (i.e. new IPs).
> >
> > However, both GoDaddy and DNS Made Easy use anycast, which makes it less
> > likely that I can see the entire picture of what's happening.
> >
> > I suspect that somewhere, one of their servers has the wrong data, or
> > some resolver is misbehaving, but based on the
> > pattern/traffic/volume/randomization of hostnames, the resolver theory is
> > less likely. I haven't analyzed the source IPs yet to see if they're in a
> > particular set of countries.
> >
> > I've opened a ticket with DNS Made Easy and they replied very quickly
> > suggesting the problem is not with them. I've opened a ticket with
> > GoDaddy and...well, it's GoDaddy, so I don't expect much (no response
> yet).
> >
> > Any ideas? Can folks try resolving eriktest.uberflip.com and post
> > here with details only if it resolves to an IP starting with 76.9 (old
> IPs)?
> >
> >
> > Thanks
> >
> > Erik
>
>
> The other likely cause of this is local cacheing nameservers somewhere
> at some ISP or major site, that do not respect TTL values for some
> reason.
>
> This is sadly a common problem - not statistically, most nameservers
> do the right thing, but if you run big sites and flip things, there's
> always a long tail of people whose nameservers just didn't get it.
>
>
>
> --
> -george william herbert
> george.herbert at gmail.com
>
>


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