Brocade Virtual ADX Global Server Load Balancing Guide (Supporting ADX v03.1.00) User Manual

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Brocade Virtual ADX Global Server Load Balancing Guide

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Transparent DNS query intercept

NOTE

In standard GSLB configuration, the Brocade Virtual ADX sends a DNS query to the DNS server to
get the IP addresses for the domain and performs health-checks on them. However in this
transparent intercept mode, where you do not do GSLB on the DNS response, the Brocade Virtual
ADX does not do these things.

NOTE

The Brocade Virtual ADX intercepts queries only for domain names configured on the Brocade
Virtual ADX. For domain names that are not configured on the Brocade Virtual ADX, the Brocade
Virtual ADX still sends queries to the authoritative DNS server.

Use the following CLI method to configure this feature.

To configure the Brocade Virtual ADX to redirect queries to an alternative DNS server, enter
commands such as the following.

NOTE

You must configure the interface IP and an IP route appropriately for the packets from Virtual ADX to
reach the authoritative DNS server.

Virtual ADX(config)#server remote-name dns-redirect 10.200.22.100

Virtual ADX(config-rs-dns-redirect)#port dns

Virtual ADX(config-rs-dns-redirect)#exit

Virtual ADX(config)#server virtual-name-or-ip dns-intercept 10.157.23.130

intercept

Virtual ADX(config-vs-dns-intercept)#port dns

Virtual ADX(config-vs-dns-intercept)#bind dns dns-redirect dns

Virtual ADX(config-vs-dns-intercept)#exit

Virtual ADX(config)#gslb dns zone brocade.com

Virtual ADX(config-gslb-dns-brocade.com)#host-info www http

Virtual ADX(config-gslb-dns-brocade.com)#exit

Syntax: [no] server remote-name name ip-addr

This command adds the alternative DNS server (the one to which you want to redirect queries). You
can enter this command multiple times for multiple alternative DNS servers.

NOTE

You can configure the alternate DNS server as a real server if it is in the same subnet as the Brocade
Virtual ADX.

Syntax: [no] port dns

This command enables the DNS port on the real server. You must use this command so that the
Brocade Virtual ADX knows you want to redirect DNS traffic to the real server (the alternative DNS
server).

Syntax: [no] server virtual-name-or-ip name ip-addr intercept

This command configures a virtual server that has the DNS server’s actual IP address. When the
Brocade Virtual ADX receives a DNS query addressed to the DNS server IP address, the Brocade
Virtual ADX intercepts the packet instead of forwarding it to the DNS server. The intercept
parameter is required and indicates that you want to use the virtual server for intercepting DNS