Brocade Communications Systems 12.4.00 Enabling DNS cache proxy, Displaying DNS cache proxy state

1 DNS cache proxy

In configurations where the ServerIron ADX and DNS server are co-located, the additional round trip time between the ServerIron ADX and DNS server is usually negligible. However, if the ServerIron ADX and DNS server are in different networks, the delay can become significant. In this case, the DNS cache proxy can help enhance performance by eliminating the exchange between the ServerIron ADX and DNS server for responses to client queries.

The DNS cache proxy feature is disabled by default. When the feature is disabled, the ServerIron ADX forwards client requests to the actual DNS server, applies the GSLB policy to the responses, then sends the optimized response to the client. In this case, the round trip time between the ServerIron ADX and DNS server is part of the overall round trip time between when the client sends the request and when the client receives the response.

If the GSLB ServerIron ADX cannot respond directly to the client for the requested domain (for example, because the domain is not configured on the GSLB ServerIron ADX), the ServerIron ADX sends the request through to the DNS server. This is the same behavior as when the DNS cache proxy feature is disabled.

NOTE

You can combine the DNS cache proxy feature with the DNS override feature (added in software release 06.0.03) to completely eliminate the separate DNS server. In this case, the ServerIron ADX contains all the required DNS information. Refer to “Combining the DNS cache proxy and DNS override features” on page 94.

Enabling DNS cache proxy

To enable DNS cache proxy, enter the following commands.

ServerIronADX(config)# gslb policy

ServerIronADX(config-gslb-policy)# dns cache-proxy

Syntax: [no] dns cache-proxy

Displaying DNS cache proxy state

To display the current GSLB policy settings, which include the DNS cache proxy state, enter the following command at any level of the CLI.

ServerIronADX(config)# show gslb policy Default metric order: ENABLE

Metric processing order:

1-Server health check

2-Remote ServerIronADX's session capacity threshold

3-Round trip time between remote ServerIronADX and client 4-Geographic location

5-Remote ServerIronADX's available session capacity

6-Server flashback speed

7-Least response selection

DNS active-only: DISABLE DNS best-only: DISABLE DNS override: DISABLE

DNS cache-proxy: ENABLE DNS transparent-intercept: DISABLE

remaining rows omitted for brevity...

Syntax: show gslb policy

The command output shown in bold type in the example indicates the DNS cache proxy state. The state can be one of the following:

92	ServerIron ADX Global Server Load Balancing Guide
	53-1002437-01