DNS flush not happening automatically

Issue

• The DNS server has an entry called myserver that is a CNAME that usually point to myserver1:

                      +---------+
               +------+myserver1|
          +----+---+  +---------+
          |myserver|
          +----+---+  +---------+
                      +myserver2|
                      +---------+

• When the CNAME myserver is changed to point to myserver2, the change is not reflected in some commands like traceroute.
• It takes ~3 hours to take effect.
• nscd is configured:

# grep -i hosts /etc/nscd.conf
# Currently supported cache names (services): passwd, group, hosts
        enable-cache            hosts           yes
        positive-time-to-live   hosts           120
        negative-time-to-live   hosts           20
        suggested-size          hosts           211
        check-files             hosts           yes
        persistent              hosts           yes
        shared                  hosts           yes
        max-db-size             hosts           33554432

• After invalidating the cache using nscd -i host, it works fine.
• Is there way that flush happens automatically without manual interference?