Brocade Communications Systems ServerIron ADX 12.4.00 - Manual (Page 34)

22 ServerIron ADX Global Server Load Balancing Guide
53-1002437-01
Proxy for DNS server
1
• IMAP4: the well-known name for port 143
• LDAP: the well-known name for port 389
• NNTP: the well-known name for port 119
• POP3: the well-known name for port 110
• SMTP: the well-known name for port 25
• TELNET: the well-known name for port 23
The <TCP/UDP-port-num> parameter specifies a TCP/UDP port number instead of a well-known
port. If the application is not one of those listed above, you still can configure the GSLB ServerIron
ADX to perform the Layer 4 health check on the specified port. If the application number does not
correspond to one of the well-known ports recognized by the ServerIron ADX, the GSLB ServerIron
ADX performs Layer 4 TCP or UDP health checks for the ports but does not perform
application-specific health checks.
Applying GSLB to CNAME records
A Canonical Name (CNAME) record is a type of DNS record that allows network administrators to
create aliases for domain names. For example, an administrator can create the following DNS
records for the Brocade domain:
• Address record: www.brocade.com, IP address 209.157.22.241
• CNAME record: www.brocade.com, alias for www.brocade.com
A CNAME record refers to another domain name instead of an IP address. A client can enter either
domain name to get to the site. In this example, each domain name goes to site 209.157.22.241.
GSLB supports CNAME records. If you configure domain names that map to other domain names,
the GSLB ServerIron ADX still will perform GSLB for the domain.
By default, the ServerIron ADX applies the GSLB policy only to zone and application names that are
configured on the ServerIron ADX. Thus, if the ServerIron ADX receives a DNS reply that contains
CNAME records for the requested zone and application, the ServerIron ADX does not apply the
GSLB policy to the CNAME records.
You can enable the ServerIron ADX to search its GSLB database for the zone and application
names in CNAME records. For example, if the ServerIron ADX receives a DNS reply that contains
the CNAME record www.brocade.com, and the zone and application name "www.brocade.com"
have been configured on the ServerIron ADX, the ServerIron ADX will apply the GSLB policy to the
CNAME record.
To enable the ServerIron ADX to apply GSLB to CNAME records, enter the following commands.
ServerIronADX(config)# gslb policy

ServerIronADX(config-gslb-policy)# dns cname-detect
Syntax: [no] dns cname-detect
NOTE
This feature does not apply to cache proxy GSLB or transparent intercept GSLB.