> On Oct 9, 2018, at 11:37 AM, endre.szabo@nanog-list-kitfvhs.redir.email wrote: > > Hey there, > > On 10/9/18 4:51 PM, Brandon Applegate wrote: >> Wanted to give a shoutout / thank you to Spectrum for this. Just noticed >> today my home PD now has dynamic/synthesized rDNS for IPv6. > > I wonder how they generate these rDNS PTR records? I was always curious, hope > someone knows. > > --
I’m guessing synthesized. There are a couple of dns servers out there that can do this. An interesting one I just found: https://all-knowing-dns.zekjur.net Also my excitement was a bit premature. It seems that: 1) This is only available from one of the resolvers given out as an IPv6 DNS server (in my region at least) - 2001:1998:f00:1::1 A dig +trace from the internet at large only gets to the NXDOMAIN (which is still much better than a SERVFAIL). 2) Looks like 2001:1998:f00:1::1 is anycasted (as one would expect). However not all of the instances will consistently return a PTR. # Simply running dig a handful of times to hit the different anycast boxes… # vom@ice:~$ dig +short @2001:1998:f00:1::1 -x 2607:fcc8:1234:5678::1234 cpe-2607-FCC8-1234-5678-0-0-0-1234.dyn6.twc.com. vom@ice:~$ dig +short @2001:1998:f00:1::1 -x 2607:fcc8:1234:5678::1234 cpe-2607-FCC8-1234-5678-0-0-0-1234.dyn6.twc.com. vom@ice:~$ dig +short @2001:1998:f00:1::1 -x 2607:fcc8:1234:5678::1234 cpe-2607-FCC8-1234-5678-0-0-0-1234.dyn6.twc.com. vom@ice:~$ dig +short @2001:1998:f00:1::1 -x 2607:fcc8:1234:5678::1234 vom@ice:~$ dig +short @2001:1998:f00:1::1 -x 2607:fcc8:1234:5678::1234 vom@ice:~$ dig +short @2001:1998:f00:1::1 -x 2607:fcc8:1234:5678::1234 cpe-2607-FCC8-1234-5678-0-0-0-1234.dyn6.twc.com. I checked 2001:1998:f00:1::1 via whoami.akamai.net and got back a handful of unique IPs. I’m guessing some inconsistent config or something else has broken on some of the instances... -- Brandon Applegate - CCIE 10273 PGP Key fingerprint: 0641 D285 A36F 533A 73E5 2541 4920 533C C616 703A "For thousands of years men dreamed of pacts with demons. Only now are such things possible."
