[dns-operations] IPv6 PTR records

Joe Greco jgreco at ns.sol.net
Sat Dec 25 01:50:57 UTC 2010

> On 17 Dec 2010, at 19:32, Chris Adams <cmadams at hiwaay.net> wrote:
> > Once upon a time, Douglas C. Stephens <stephens at ameslab.gov> said:
> >> A case in point is SSHd.  Many of the other sites running
> >> SSHd to which my customers connect are using versions of SSHd which
> >> stall and time-out if PTR records for my client-side IPs are not
> >> available.
> > 
> > I've not seen that behavior from OpenSSH (or any other server for that
> > matter).  It may stall if lookups don't return (e.g. bad DNS server,
> > broken network, etc.), but an NXDOMAIN doesn't cause any slowdown.
> Yes, the cause of the delay is more likely to be ident lookup timeouts.

I don't know about "more likely;" I see plenty of misconfigured PTR's
at hotspots, hotels, and assorted other remote points.  Between that
and various crummy NAT and firewall issues, it's easier to connect via
VPN and *then* ssh.  :-)

... JG
Joe Greco - sol.net Network Services - Milwaukee, WI - http://www.sol.net
"We call it the 'one bite at the apple' rule. Give me one chance [and] then I
won't contact you again." - Direct Marketing Ass'n position on e-mail spam(CNN)
With 24 million small businesses in the US alone, that's way too many apples.

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