Section A: Planning summary for DNS configuration

Determine DNS configuration

Configuring DNS will be faster if you plan ahead. Use the information in the following table to determine the DNS configuration that is necessary for your organization.

Decisions to make	Your options	Considerations
Whether you need to change basic DNS configuration	Appliance Domain DNS Nameservers	Typically organizations do not change nameservers and appliance domain. However, if the DNS nameservers that your NetCache appliance is to use changes, or the appliance is moved and, therefore, its domain name changes, you can change this information in the NetCache configuration.
Whether you need support for domain names that are not fully qualified	DNS Tree-Search Enable DNS Search Paths	System administrators of enterprises should consider configuring NetCache to handle domain names that are not fully qualified. ISPs usually do not need to configure support for domain names that are not fully qualified because their users typically enter fully qualified domain names in URLs.
Whether it is beneficial to reduce the number of DNS lookups performed by remote DNS nameservers	Hosts File	Typically, you add entries to this option only if you have a special requirement to bypass the DNS nameserver.
Whether you want clients to send DNS queries to the NetCache appliance instead of directly to DNS nameservers	DNS caching options	If the NetCache appliance is configured to function as a DNS proxy cache, the appliance can resolve a DNS query without contacting the DNS nameserver if the appliance has the host name to IP address mappings in its cache.
Whether you need to support internal resolvers that cannot handle external host names	Two methods are available: Split DNS Per Domain mapping (Domain-to-Nameserver-Mapping option)	Runtime issues and configuration requirements differ for the two methods. You must consider both issues when determining the right strategy for your organization. See Supporting internal resolvers that cannot handle external host names for more information.
Whether you need to reduce the load of DNS queries on your organization's internal resolvers	DNS iterative resolution options	When this feature is enabled, NetCache functions as a full-service resolver.
Whether you need DNS records in the NetCache DNS cache to expire before the server-assigned TTL expires	Per-Domain TTL Expiration option	In a DHCP-DDNS environment in which IP addresses are dynamically assigned, you might want to expire DNS records in the NetCache DNS cache before the server-assigned TTL expires.