DNSCacheTimeOut defines maximum amount of live time of a DNS cache entry, in seconds.
When resolving host names during crawling, indexer stores the results of the DNS server responses into a into a built-in DNS cache. This is done for performance purposes. However, it can negatively affect crawling of the distributed sites residing on multiple IP. By changing the DNSCacheTimeOut to a small value this negative effect can be reduced (at the expense of possibly slower resolution speed).
The default value is 3600 seconds.