Let’s go through some common real-world DNS problems. Many of these problems are easy to recognize and correct. We cover these problems as a matter of course—they’re some of the most common problems because they’re caused by some of the most common mistakes. Here are the contestants, in no particular order.
This particular problem will occur only if you make changes to your zone data file by hand, without using the DNS console. The DNS console remembers to increment the serial number in the SOA record each time it changes zone data, so you don’t have to worry about it. However, this also means that you probably won’t be in the habit of updating the serial number, so you may forget when making that one-off manual modification.
The main symptom of this problem is that slave name servers don’t pick up any changes you make to the zone on the primary server. The slaves think the zone data hasn’t changed since the serial number is still the same.
How do you check if you remembered to increment the serial number? Unfortunately, that’s not so easy. If you don’t remember what the old serial number was and your serial number gives you no indication of when it was updated, there’s no direct way to tell whether it has changed. When you start the primary, it will load the updated zone data file regardless of whether you’ve changed the serial number. About the best you can do is to use nslookup to compare the data returned by the ...