Brocade Virtual ADX Global Server Load Balancing Guide (Supporting ADX v03.1.00) - Manual (Page 137)

Brocade Virtual ADX Global Server Load Balancing Guide 127
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Chapter
2
Global Server Load Balancing for IPv6
Global Server Load Balancing for IPv6 overview
Global server load balancing (GSLB) enables a Brocade Virtual ADX to add intelligence to
authoritative Domain Name System (ADNS) servers by serving as a proxy to these servers and
providing optimal IP addresses to the querying clients. As a DNS proxy, the GSLB Brocade Virtual
ADX evaluates the IP addresses in the DNS replies from the ADNS and places the “best” host
address for the client at the top of the DNS response. The GSLB Brocade Virtual ADX can also
directly respond to the DNS queries in the DNS cache proxy with DNS override mode.
As data centers increasingly move towards migrating some or all of their servers and services to
IPv6, there is an increasing need to perform GSLB for these IPv6 entities in addition to IPv4.
Brocade GSLB Brocade Virtual ADX performs GSLB for both IPv4 (A records) and IPv6 (AAAA
records) and directs the clients to the optimal IP address based on the configured GSLB policies.
The GSLB Brocade Virtual ADX supports global server load balancing and redundancy for IPv6
addresses in DNS cache proxy and DNS override mode only. In this mode, the IPv6 addresses for
hosts are configured on the Brocade Virtual ADX GSLB controller, which acts as the ADNS server for
the configured zones. The GSLB controller does not have a back-end DNS server. Instead, the GSLB
controller intercepts DNS queries and generates the DNS response by applying GSLB policies on
the IPv6 list configured for the host name.
The GSLB controller ensures that a client always receives a DNS reply for a host site that is the best
choice among the available hosts. Just as with data centers in which the content for a domain can
be serviced by IPv4 and IPv6 servers, a domain on the GSLB Brocade Virtual ADX can have a mix of
IPv4 and IPv6 domain IP addresses. If the client makes an A record query, then the best IPv4
domain IP address will be selected for the client. Similarly, if the client makes an AAAA query, then
the best IPv6 domain IP address will be selected for that client.
By default, when you enable the IPv6 GSLB controller function, the Brocade Virtual ADX disables
the optimization for IPv6 traffic processing which prevents the enabling of IPv6 SSL offload
function available in IPv6 optimized mode only. You can enable IPv6 path optimization with GSLB
enabled to allow IPv6 GSLB and SSL offload on same device.
Brocade Virtual ADX GSLB for IPv6 configuration tasks are covered in four sections within this
chapter:
• Basic GSLB for IPv6 configuration: Basic configuration tasks include the configuration of the
GSLB Brocade Virtual ADX and the site Brocade Virtual ADXs to support GSLB of IPv6
addresses. This configuration includes the configuration of a virtual IP address (VIP) for the
ADNS, the configuration of DNS cache proxy mode with override lists, the definition of zones
and sites on the GSLB ADX device, and the preserving of the optimized IPv6 path for IPv6
GSLB. The GSLB protocol must be enabled on the site ADX device.
• Advanced GSLB for IPv6 configuration: Advanced configuration tasks include the configuration
of GSLB policies and sticky persistence for IPv6 addresses.