Brocade Communications Systems 12.4.00 Manual De Usuario

DNS cache proxy

1

The Direct response field, under “DNS cache proxy stat”, lists how many DNS queries the GSLB 
ServerIron ADX has responded to using the DNS cache proxy feature instead of forwarding the 
queries to the DNS server. In this example, the GSLB ServerIron ADX has responded directly to 
client queries ten times with the best site address among those cached on the ServerIron ADX 
itself, instead of forwarding the request to the DNS server. 

For information about the statistics in the DNS query intercept stat section, refer to 

 on page 101.

Combining the DNS cache proxy and DNS override features

When the DNS cache proxy feature is enabled, the GSLB ServerIron ADX has to query the 
authoritative DNS server at regular intervals, to refresh the IP address list for each domain 
configured for GSLB. You can eliminate the need for a backend DNS server, by combining the cache 
proxy feature with the DNS override feature.

When you enable the DNS override feature, you also need to configure an IP list for the required 
domains. The ServerIron ADX performs health checks on the IP addresses configured for the 
domains and directly responds to client queries by using the GSLB policy to select the best IP 
address from the IP list configured for the requested domain.

By combining the DNS cache proxy feature with the DNS override feature, you can configure the 
ServerIron ADX to directly respond to client requests, without ever consulting the authoritative DNS 
server. 

NOTE

A GSLB ServerIron ADX does not contain all the features of a real DNS server and thus cannot 
completely replace the DNS server.

NOTE

Although you do not need a real DNS server when you combine DNS cache proxy with DNS override, 
you still need to configure a virtual IP address for the DNS server. Clients send queries to the virtual 
IP address. 

For information about configuring DNS cache proxy, refer to 

 on page 91. For 

information about configuring DNS override, see 

To add a virtual IP address to which the clients can send their DNS queries, enter a command such 
as the following:

ServerIronADX(config)# server virtual-name-or-ip dns-proxy 209.157.23.87



ServerIronADX(config-vs-dns-proxy)# port dns

The command in this example adds IP address 209.157.23.87 as a virtual server. When clients 
send their DNS queries to this address, the ServerIron ADX processes the queries.

GSLB DNS type any query

DNS servers perform the translation between fully qualified domain names and IP addresses. DNS 
supports a number of record types such as IPv4 Address records (A records), IPv6 Address records 
(AAAA records), Name Server records (NS records), Mail Exchange (MX records), Canonical Name 
records (CNAME records) and so on.