Sapo, DNS and (real) dynamic A records

Published at Sun 06 April, 2008 11:33 | Permalink Permalink | Comments Comments (3) | Trackbacks Trackbacks (0)

So lately, I am having problems accessing my 0x82.com at home. This domain sits on a dynamic IP address, and I use editdns to update the DNS records.

EditDNS advertises my A record with a 0 TTL. However, I found that my ISP Sapo caches the record with a huge TTL:

0x82.com.        604800    IN    A    82.155.174.2

Before I shout “what th f0ck are wrong with this guys”, I still have to do a quick read of the relevant RFC, because I think that a 0 TTL may not be a “standard” thing…

As always, if you know something about this, please shoot! :-)

Tags dns sapo

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  1. avatar David Negreira Sun 06 April, 2008 13:27

    Probably it’s just a protection against dns update flooding, as it does not make any sense to check when a domain expires every second.

  2. avatar Gonçalo Silva Mon 07 April, 2008 02:28

    There are some ISPs that ignore the TTL sugestion give by the authority nameserver if this value is to short. It´s seems sapo is one of them.

  3. avatar Yannick Tue 08 April, 2008 15:33

    According to Cricket Liu books: “Unfortunately, TTLs of zero tickle a bug in some older name servers, which age out the records before returning them to the resolver that initiated the query. D’oh!”

    Not sure what is in the RFC… ;)

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