Bind fails to resolve external IPv4 recursive queries periodically in RHEL

Solution Unverified - Updated -

Issue

  • Two of the nameservers in a particular data center are slow to resolve  some external recursive IPv4 record queries or time out, and  will eventually require restarting the named service before they can  successfully resolve A records in "problem" domains again.
  • Occurs consistently with some "problem" domains, and sporadically with  other domains.  Specific examples of "problem" domains include  www.example.com, www.example.com and others.
  • Impact: This causes mail to fail to be delivered in the event one of the  failed queries is in response to an MX lookup.
  • The problem is more apparent on A records with very short TTL  (time to live) values since they cannot be cached longer than  the TTL allows.
  • Using nscd flush has no effect.

Environment

  • Red Hat Enterprise Linux (RHEL) 
    • Note: Since this is a network issue, this issue can occur with any RHEL release..
  • bind nameserver configured to perform recursion of external records for clients
  • bind configuration (/etc/named.conf - zone declarations omitted)

    options {
                
                   directory "/";
                   allow-transfer { trustedslaves; };
                   allow-recursion { recursive; };
           
                   auth-nxdomain no;
           
                   version "cowbell++";
                
                   max-ncache-ttl 10;
                
                   statistics-file "/var/log/named.stats";
                   memstatistics-file "/var/log/named.memstats";
                   zone-statistics yes;
                
                   dump-file   "/var/log/named.dump";
                
                   recursing-file "/var/log/named.recursing";
                
                   querylog yes;
                
                   notify no;
                   listen-on port 53 {
                       any;
                   };
                };

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