Brocade Virtual ADX Global Server Load Balancing Guide (Supporting ADX v03.1.00) - Manual (Page 84)

74 Brocade Virtual ADX Global Server Load Balancing Guide
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Transparent DNS query intercept
1
The commands are the same as the ones for configuring the Brocade Virtual ADX to redirect
queries directly to another DNS server, with one difference. The command that enables the DNS
port on the real server (the other ADX device) uses the proxy parameter. This parameter indicates
that the Brocade Virtual ADX needs to perform GSLB on the response before sending the response
back to the client.
Responding to queries directly
To configure transparent DNS query intercept to directly respond to queries using IP addresses
configured on the Brocade Virtual ADX, do the following:
• Configure a virtual server with the IP address of the authoritative DNS server that you want to
intercept.
• Specify the domain name and host application for which you want to intercept queries.
• Enable the DNS transparent intercept feature.
• Enable the dns transparent-intercept command in the GSLB policy.
NOTE
In the direct-response mode, the Brocade Virtual ADX uses GSLB to pick the best address by default.
No additional configuration is needed to further enable GSLB.
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.
To configure the Brocade Virtual ADX to respond to queries using a set of IP addresses configured
on the Brocade Virtual ADX itself, enter commands such as the following.
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)#gslb dns zone brocade.com
Virtual ADX(config-gslb-dns-brocade.com)#host-info www http
Virtual ADX(config-gslb-dns-brocade.com)#host-info www ip-list 10.200.1.1
10.200.1.2 10.200.1.3 10.200.1.4 10.200.1.5
Virtual ADX(config-gslb-dns-brocade.com)#exit
Virtual ADX(config)#gslb policy
Virtual ADX(config-gslb-policy)#dns transparent-intercept
These commands configure a virtual server for the authoritative DNS server IP address, specify the
zone and host names for which to intercept queries, and specify the IP addresses to use in
responses to the queries. The commands also enable the DNS transparent intercept feature and
enable the Brocade Virtual ADX to examine incoming DNS packets.
NOTE
For non-direct respond transparent intercept, you should not enable dns transparent-intercept in the
gslb policy.
Notice that unlike the types of transparent DNS query intercept shown in “Redirecting queries” on
page 71, the type shown here does not require configuration of a real server. Since the Brocade
Virtual ADX in this case is responding directly to the query instead of redirecting the query to
another device, only the virtual server for intercepting the queries is required.