Section A: Planning for interaction with a back-end DNS nameserver

Configuring the GRM DNS server to resolve non-CDN DNS queries

The GRM DNS server must proxy some DNS queries. The GRM DNS server resolves local DNS queries only for FQDNs associated with the CDN network (GRM domains). Queries for FQDNs not serviced by the GRM DNS server and zone transfers are proxied by the GRM DNS server to the back-end DNS nameserver.

To enable the GRM DNS server to proxy these DNS requests, you must configure it to use the back-end DNS nameserver as its nameserver. You do so either by listing the back-end DNS nameserver in the Nameservers option or the Domain-to-Nameserver Mapping option on the DNS - General page in the Appliance Manager.

GRM DNS server acting as the authoritative DNS server for content provider domains

A GRM DNS server can assume the identity of the existing authoritative DNS nameserver for the CDN name space, that is, the GRM DNS server can assume the IP address that was previously assigned to the authoritative DNS nameserver. The authoritative DNS nameserver is then reconfigured with a new IP address.

If you want the GRM DNS server to act as the authoritative DNS server for content provider domains, you must do one of the following:

You must configure the GRM DNS server to take over the IP address that was previously assigned to the authoritative DNS nameserver. You must reconfigure the authoritative DNS nameserver with a new IP address.
You must change the DNS hierarchy to point to the GRM DNS server.

If multiple back-end nameservers exist for a GRM DNS server, the GRM DNS server can assume the identity of the back-end nameservers (with IP address aliasing). If you cannot use IP address aliasing, you can change the IP address of the back-end nameserver to that of the GRM DNS server in the DNS hierarchy.

Note
Some GRM deployments do not require the GRM DNS server to handle all DNS requests for the CDN namespace. See Section B, Planning for supporting queries for CDN content for more information.

Assigning an additional IP address with the Appliance Manager

Assigning an additional IP address to an interface (called an alias) enables you to administer the GRM DNS server by its standard host name, instead of by the host name assigned to the back-end DNS nameserver. See the online Help for information about how to assign an alias to an interface.

Supporting multiple back-end nameservers in different domains

Multiple DNS nameservers can serve as back-end nameservers for one GRM DNS server. This feature enables you to store content from different domains on different back-end nameservers. For example, one back-end nameserver for a GRM DNS server could store content for domain abc.com, and another back-end nameserver could store content for lmn.com.

If your deployment includes multiple back-end nameservers for a GRM DNS server and those nameservers store content from different domains, you must configure the GRM DNS server to associate specific back-end nameservers with particular domains. The GRM DNS server can then provide GRM agent caches with information to enable them to determine which back-end DNS nameserver should receive the content miss.

Note
A back-end nameserver for a GRM DNS server can be in the same location as the GRM server. Alternatively, a back-end nameserver can be in a different location, and the GRM DNS server can point to it.

DNS setup to support proximity measurements

If you are using a GRM DNS server, make sure that you have configured DNS so that DNS queries are sent directly to the authoritative DNS nameserver instead of relying on recursion as a way for DNS queries to reach the authoritative DNS nameserver. Otherwise, the GRM DNS server cannot obtain accurate proximity information.