Brocade Communications Systems ServerIron ADX 12.4.00 - Manual (Page 13)

ServerIron ADX Global Server Load Balancing Guide 1
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Chapter
1
Global Server Load Balancing
Global Server Load Balancing overview
Global Server Load Balancing (GSLB) enables a ServerIron ADX to add intelligence to authoritative
Domain Name System (DNS) servers by serving as a proxy to these servers and providing optimal IP
addresses to the querying clients. As a DNS proxy, the GSLB ServerIron ADX evaluates the IP
addresses in the DNS replies from the authoritative DNS server for which the ServerIron ADX is a
proxy and places the “best” host address for the client at the top of the DNS response.
NOTE
The server no-remote-l3-check command disables Layer3 health checks of IPs learned through
GSLB.
NOTE
You need to increase max virtual servers to 1024, max real servers to 2048 and max ports to 4096
to use the max hosts/zone feature.
Do not increase following when use max zone/host feature, or you will run out of memory.
system-max ip-static-arp 4096
system-max l3-vlan 4095
system-max mac 64000
system-max ip-route 400000
system-max ip-static-route 4096
system-max vlan 4095
system-max spanning-tree 128
system-max session-limit 1000000
system-max virtual-interface 4095
GSLB provides the following advantages:
• No connection delay
• Client geographic awareness based on DNS request origination
• Distributed site performance awareness
• Fair site selection
• Statistical site performance measurements that minimize impact of traffic spikes
• Best performing sites get fair proportion of traffic but are not overwhelmed
• Protection against "best" site failure
• Straight-forward configuration
• All IP protocols are supported
In standard DNS, when a client wants to connect to a host and has the host name but not the IP
address, the client can send a lookup request to its local DNS server. The DNS server checks its
local database and, if the database contains an Address record for the requested host name, the
DNS server sends the IP address for the host name back to the client. The client can then access
the host.