By default, the ProxySG appliance caches negative DNS responses sent by the DNS server. You can configure the length of time, or the  time-to-live (TTL) value,  for which a negative DNS response is cached. By default, the ProxySG appliance uses the TTL value returned by the DNS server.

To modify the time for caching of negative responses, use the following command from the (config) prompt:

SGOS#(config) dns negative-cache-ttl-override <seconds>

- where the seconds field accepts any integer between 0 and 600 seconds.

- setting the TTL setting to a non-zero value overrides the TTL value from the DNS response.

To disable caching of negative responses, use the following command from the (config) prompt:

SGOS#(config) dns negative-cache-ttl-override 0

- setting the TTL value to 0 seconds disables negative DNS caching.

To restore the default value for  caching DNS negative responses, use the following command from the (config) prompt):

SGOS#(config) dns no negative-cache-ttl-override