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Free eBook: Alternative DNS Servers

Paul Ooi — Fri, 25 Feb 2011 13:32:36 +0000

Grab this 747 pages DNS eBook for Free; Written by Jan-Piet Mens, titled “Alternative DNS Servers”. I glance through at the eBook and found several interesting topics for DNS deployments.

Bind DLZ – The Bind extension which can store your data in database MySQL, PostgreSQL and etc.
NSD – A lot people didn’t know about Name Server Daemon, find out more from the eBook.
DNS Planning – Name Server deployment planning, capacity planning and how to scale.
PowerDNS – Configure and master it.
LDAP DNS – Deploy DNS server with LDAP.

Alright, enough with the talks, where to download the eBook? It’s FREE for Download here

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How to Find Your Closest Anycast DNS Server with Dig

Paul Ooi — Wed, 23 Feb 2011 00:53:02 +0000

Most ISP deploys Anycast DNS server on their network and bring the closest DNS server to their user for DNS resolver. You may see a DNS server with a single IP Address but there are multiple DNS Servers running on different geographical location.

So which DNS server do you resolve it from? For example we run a query on DNS F Root Server


$ dig @f.root-servers.net hostname.bind  txt ch +short
"lga1a.f.root-servers.org"

On the result, it shows that I am using lga1a.f.root-servers.org as resolver. Some DNS server does reply “chaos” (ch) request but some refuse; for example Google DNS and Open DNS Server. So if your ISP is running Anycast DNS, you can try to lookup where is the DNS server locate.

There is another command perform checking via “id.server” query, it only helpful when the DNS has server-id configured.


dig @k.root-servers.net id.server txt ch +short
"k2.tokyo.k.ripe.net"

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Reverse DNS Lookup with Dig

Paul Ooi — Sat, 22 Jan 2011 11:51:28 +0000

Reverse DNS, in simple explanation it means that resolve your IP address into hostname. Nowaday it became a must have requirement for mail server’s IP address. It is also one of the method to determine your mail server IP is glue to the hostname.

Here is how to find out the reverse DNS IP address is pointed to which DNS server for zone delegation.


dig -x 175.136.188.90

; <<>> DiG 9.6.0-APPLE-P2 <<>> -x 175.136.188.90
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NXDOMAIN, id: 21938
;; flags: qr rd ra; QUERY: 1, ANSWER: 0, AUTHORITY: 1, ADDITIONAL: 0

;; QUESTION SECTION:
;90.188.136.175.in-addr.arpa.   IN      PTR

;; AUTHORITY SECTION:
136.175.in-addr.arpa.   10800   IN      SOA     ns1.tm.net.my. dnsadm.tmnet.com.my. 2011012113 10800 3600 604800 86400

;; Query time: 37 msec
;; SERVER: 192.168.0.1#53(192.168.0.1)
;; WHEN: Sat Jan 22 19:39:12 2011
;; MSG SIZE  rcvd: 111

The result above shown

The SOA record shown the IP Address is pointed to ns1.tm.net.my for reverse DNS delegation.
The zone 136.175.in-addr.arpa is delegating the IP 175.136.188.90

This command is pretty useful when you want to find out is the reverse DNS delegation works correctly.

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