Intel 1520 ユーザーズマニュアル

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Chapter 4 Configuring the Appliance
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Configuring the host database
The appliance host database stores the domain name server (DNS) entries of 
servers that the appliance contacts to fulfill user requests. You configure the 
appliance host database by setting options in the Host Database Management 
section. The following table describes the options.
Option 
Description 
Lookup timeout
Specifies the DNS lookup timeout in seconds. You can 
choose from the following:
5 seconds
10 seconds
15 seconds
20 seconds
30 seconds
Foreground 
timeout
Specifies how long DNS entries can remain in the database 
before they are flagged as stale. You can choose from the 
following:
12 hours
24 hours
48 hours
For example, if this timeout is 24 hours, and a user requests 
an entry that has been in the database for 24 hours or longer, 
the appliance will refresh the entry before serving it. 
You can set the background timeout (see next item) to refresh 
entries in the background, before objects become stale.
Be careful not to set the foreground timeout too low. Doing so 
might slow response time. Additionally, setting the timeout 
value too high risks accumulation of incorrect information. 
Setting the foreground timeout to greater than or equal to the 
background timeout disables background refresh.