As was previously mentioned, you need to be more clear about what you're asking. There are multiple related concepts. Look up a description of the SOA record, in particular the refresh, retry, expire, and minimum TTL fields. The first three affect how DNS secondary servers behave. The last can affect client responses, but you can also have per-record TTL values and zone default TTL values. This link might be a good starting point for understanding the SOA parameters: <http://rscott.org/dns/soa.html> If you're trying to solve a problem with DNS secondaries keeping up, watch that you're incrementing the serial number. If you're using split zones (views) or other esoteric configurations, things get a whole lot more complicated. -- Everyone has a photographic memory. Some don't have film. - Steven Wright