Configure the Asus RT-AC66U Router as a Caching DNS Server with Bind

asus-rt-ac66u

Introduction

In this article I am going to walk you through the necessary steps to configure your Asus RT-AC66U as a caching dns server using bind.¬†According to Wikipedia“Caching name servers (DNS caches) store DNS query results for a period of time determined in the configuration (time-to-live) of each domain-name record. DNS caches improve the efficiency of the DNS by reducing DNS traffic across the Internet, and by reducing load on authoritative name-servers, particularly root name-servers. Because they can answer questions more quickly, they also increase the performance of end-user applications that use the DNS. Recursive name servers resolve any query they receive, even if they are not authoritative for the question being asked, by consulting the server or servers that are authoritative for the question. “

As you must already know,¬†the Asus RT-AC66U runs Busybox, which is a very small but powerful embedded Linux distro. Because of this there are a lot of familiar commands available via the CLI. However, don’t get to comfortable, as this is still a very foreign land.

Note that this article assumes that you have ssh or telnet working and can log into your RT-AC66U via the CLI.

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Bind – Zone File Serial Number Reset

Lemo-the-worm Each and every zone file has a unique serial number and that serial number should increment with each subsequent revision

A serial number is traditionally in the format (YYYYMMDDSS) where SS the sequence number. For example, today is 1/21/2011, so the serial number in a zone file modfied today would be… 201101210.

So lets say that you pushed that zone today and when you went back to make an additional change, you accidentally added an additional number to your serials and instead of  201101211 you ended up with 2201101211.

In order to get everything back in order you will need to manually reset the zone file's serial number by setting it to the number below. Its highest number you can get using 32 bits.

4294967295

To to reset your serial number, update your zone file with the serial number listed above and push it out to the slaves. Then change your zone files serial number back to the correctserial number, which will be considered to be greater than the magic number above. Then push dns again.

Check your slave servers and verify the the zone file now has the correct serial.