[Pdns-users] DNS Failover

Nikolaos Milas nmilas at admin.noa.gr
Fri Apr 19 09:16:57 UTC 2013


We have two SMTP/POP/IMAP/Apache(Webmail) Servers, say mail1.example.com 
and mail2.example.com and we want to implement DNS-based failover. 
mail1.example.com is the main one; in case of mail1.example.com failure, 
DNS should redirect users as soon as possible to mail2.example.com.

Is there a suggested/pre-designed way to do it?

As I understand, we could:

 1. Have a CNAME record like mail.example.com which maps users to
    mail1.example.com, using a low TTL like 30 sec.
 2. Monitor mail1.example.com every couple of seconds (e.g. using pings).
 3. In case of no reply by mail1.example.com, change (via script) the
    CNAME record to now map mail.example com to mail2.example.com.

(Note: We are using pdns 2.9.22 with LDAP backend, but this is irrelevant.)

Can you please provide advice on how to handle this best?


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