reverse DNS servfail

[Danny Mayer]

/dev/rob0 wrote:
> A customer of mine just today got a new ISP. The new IP is 
> 69.15.253.106. At this time the reverse lookup is failing:
> $ host 69.15.253.106
> Host 106.253.15.69.in-addr.arpa not found: 2(SERVFAIL)
> $ host -tns 253.15.69.in-addr.arpa
> Host 253.15.69.in-addr.arpa not found: 2(SERVFAIL)
> $ host -tns 15.69.in-addr.arpa
> Host 15.69.in-addr.arpa not found: 2(SERVFAIL)
> 
> I asked the ISP (cbeyond.net) for RFC 2317, section 5.2, classless rDNS 
> delegation: with CNAMEs pointing to PTR records in our forward zone. (I 
> do have and can query the PTR's corresponding to my CNAME requests.) The 
> customer service people talked to their "DNS engineers" [snicker] who 
> told them to tell me:
>      "Our DNS Engineers have stated that Cbeyond's DNS service does
>       not support this form of classless addressing."
> Before I asked, I tested and got NXDOMAIN on this IP. Now it's SERVFAIL.
> 
> Before I approach the "DNS engineers" I want to know a bit more.
> 
> 1. Is there a way to tell if they're running BIND?
>     a. If so, why would it "not support" RFC 2317 classless delegation?
>     b. If not, can this be true? Maybe in their junkware the in-addr.arpa
>        zones are hard-coded to only allow PTR records?
> 2. Is there a way to tell from the outside why they're getting SERVFAIL?
> 3. Is anyone else familiar with Cbeyond in particular?
> 
> Oh, I looked up another IP in Cbeyond's block, and it wasn't SERVFAIL. 
> These are the servers:
> $ host -tns 20.15.69.in-addr.arpa
> 20.15.69.in-addr.arpa name server infinity.cbeyond.net.
> 20.15.69.in-addr.arpa name server to.cbeyond.net.
> 20.15.69.in-addr.arpa name server beyond.cbeyond.net.
> 
> I don't understand why I can get 20.15.69.in-addr.arpa but I can't get 
> 15.69.in-addr.arpa.

They are running BIND 9.3.1-NT1 so they do support RFC 2317 classless 
delegation. 15.69.in-addr.arpa is delegated to them but nothing seems to 
be set up beyond that. It looks like they have something misconfigured, 
hence the error messages.

Danny