HP ProCurve Secure 7000dl Series Basic Management And Configuration Manual page 574

Domain Name System (DNS) Services
Troubleshooting DNS
N o t e
Step
1. The router receives a
request to translate a
hostname.
2. If the hostname is in the
local host table, the router
sends its IP address to the
client.
3. If the hostname is not in
the table, the router
queries its own DNS
server.
4. If the server can translate
the name, the router
forwards the response to
the client.
5. If the server cannot
translate the name, the
router appends the default
domain name to the
request and resends it.
6. If the server can translate
the name, the router
forwards the response to
the client.
12-12
You can also start displaying the debug messages from any mode context with
the do command.
Then, have the DNS client again attempt to access the host. Track the router's
activity. It should pass through the steps shown in Table 12-1. Determine where
the process breaks down and troubleshoot the problem accordingly.
Table 12-1. DNS Proxy Process
IP.DNS PROXY Messages
Received request from
<DNS client>
Serving reply for
"<hostname>" from host
database: <host A.B.C.D>
Forwarding query for
"<hostname>" to <DNS
A.B.C.D>
• Received response from
server
• Transmitting response to
<DNS client>
Forwarding query for
"<hostname>.<default
domain name>" to <DNS
server A.B.C.D>
• Received response from
server
• Transmitting response to
<DNS client>
Likely Problem If The
Message Does Not Appear
DNS proxy is not enabled.
The host table does not
include the hostname.
You have not specified at
least one external DNS
server.
• The external server
cannot translate the
hostname.
• The router cannot reach
the external server.
You have not configured a
default domain name.
• The external server
cannot translate the
hostname.
• The router cannot reach
the external server.
Likely Problem If The
Message Repeats
The router cannot resolve
the hostname. (See Steps 2,
3, and 5 for possible causes.)
——
• The external server
cannot translate the
hostname.
• The router cannot reach
the external server.
——
• The external server
cannot translate the
hostname.
• The router cannot reach
the external server.
——