1. A S I A P A C I F I C N E T W O R K I N F O R M A T I O N C E N T R E APNIC Open Address Policy Meeting What is Reverse DNS October 26th, Brisbane Bruce Campbell bruce_campbell@apnic.net

2. A S I A P A C I F I C N E T W O R K I N F O R M A T I O N C E N T R E What is ‘Reverse DNS’?  ‘Forward DNS’ maps names to numbers  svc00.apnic.net -> 202.12.28.131  ‘Reverse DNS’ maps numbers to names  202.12.28.131 -> svc00.apnic.net

3. A S I A P A C I F I C N E T W O R K I N F O R M A T I O N C E N T R E IPv4 - in-addr.arpa  Hierarchy of IP addresses  Use ‘in-addr.arpa’ domain  INverse ADDRess  IP address is written L to R  202.12.28.131  Reversed in in-addr.arpa hierarchy  131.28.12.202.in-addr.arpa

4. A S I A P A C I F I C N E T W O R K I N F O R M A T I O N C E N T R E IPv4 in-addr.arpa tree whois 202 203 210 211.. 28.12.202.in-addr.arpa Root DNS (‘.’) educomarpaphnet apnic in-addr  Mapping numbers to names - ‘reverse DNS’ 12 28

5. A S I A P A C I F I C N E T W O R K I N F O R M A T I O N C E N T R E IPv6 ip6.int  Like IPv4 in-addr.arpa, just lots more numbers to deal with  2001:218::/35  0.8.1.2.0.1.0.0.2.ip6.int  1.8.1.2.0.1.0.0.2.ip6.int

6. A S I A P A C I F I C N E T W O R K I N F O R M A T I O N C E N T R E IPv6 ip6.arpa ?  RFC1883 (and ip6.int) eventually Historic  RFC2874 defines ip6.arpa  Depends on new DNS features  DNAME, BITLBL  ip6.arpa not yet delegated  Not yet in use  APNIC only supports ip6.int at present time.

7. A S I A P A C I F I C N E T W O R K I N F O R M A T I O N C E N T R E SOA Record 28.12.202.in-addr.arpa IN SOA machine.that.is.primary.NS myself.my.address ( 2000030201; SOA Serial Number ; YYYY MM DD XX 3H; Refresh time 30M; Retry time 2W; expiry 12H ); minimum Time To Live (TTL)

8. A S I A P A C I F I C N E T W O R K I N F O R M A T I O N C E N T R E NS Records ; Still in ‘28.12.202.in-addr.arpa’ IN NS ns1.my.forward.domain. ; See RFC 1035 IN NS ns2.my.forward.domain. ; At least two nameservers IN NS ns.some.faraway.site. ; See RFC 2182 - backup in ; case your site is down

9. A S I A P A C I F I C N E T W O R K I N F O R M A T I O N C E N T R E PTR Records ; PTR records ‘point’ an IP to a hostname ; In current $ORIGIN, 28.12.202.in-addr.arpa 131IN PTR svc00.apnic.net ; IP address 202.12.28.131 190IN PTR jp-gw.apnic.net ; IP address 202.12.28.190

10. A S I A P A C I F I C N E T W O R K I N F O R M A T I O N C E N T R E Always Remember the Dot.  Forgetting the trailing dots is bad  BIND appends the current domain ($ORIGIN) to a record without a trailing dot Zone file entry 3 IN PTR machine.no.dot $ host 202.12.28.3 3.28.12.202.IN-ADDR.ARPA domain name pointer machine.no.dot.12.12.202.in-addr.arpa

11. A S I A P A C I F I C N E T W O R K I N F O R M A T I O N C E N T R E DNS Books Images copied from http://www.ora.com/ and Copyright O’Reilly and Associates

12. A S I A P A C I F I C N E T W O R K I N F O R M A T I O N C E N T R E Questions?  Dns-admin@apnic.net