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refused = query refused
servfail = server failure
NOTE
Do not change the error code unless you are absolutely certain of the effect of the configuration. For
example, if you configure nxdomain as the return code, the GSLB ServerIron ADX responds to an
unsupported query type with this error code. When the client receives the nxdomain response, the
client typically stops attempting to resolve any other record type for that name. For example, an
nxdomain response to an IPv6 record type might stop the client from sending a query for an IPv4
record type, even though IPv4 record types exist for that domain. Furthermore, if this response (with
nxdomain rcode) is negatively cached, it can result in a potential denial-of-service attack for a
particular domain name.
Viewing error handling statistics
You can view the number of client requests for unsupported DNS record types for which the GSLB
ServerIron ADX generated an error handling response. Enter the following command at any level of
the CLI.
ServerIronADX(config)# show gslb global-stat
DNS cache proxy stat:
Direct response
DNS query intercept stat:
Redirect
Unsupported query types stat:
Error handling cnt
In the example above, the Error handling cnt shows that the GSLB ServerIron ADX generated and
sent error handling responses for three client queries.
Syntax: show gslb global-stat
Clearing the error handling statistics
To clear the error handling statistics for the GSLB ServerIron ADX, enter the following command.
GSLB-ServerIronADX# clear gslb unsupported-response-cnt
Syntax: clear gslb unsupported-response-cnt
To confirm the statistics were cleared, use the show gslb global-stat command.
ServerIron ADX Global Server Load Balancing Guide
53-1002437-01
GSLB error handling for unsupported DNS requests
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Direct response
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