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The timers that are associated with the entire zone are set in a special record called the Start of Authority (SOA), at the beginning of the zone file. It can be examined by querying the nameserver; for example:
| Code Block |
|---|
% dig \-t soa uoregon.edu |
...
uoregon.edu. 86400 IN SOA localhost.uoregon.edu. |
...
hostmaster.uoregon.edu. 2009120709 7200 900 605000 86400 |
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Those fields are: |
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root name of the zone: uoregon.edu. |
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TTL: |
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86400 class: IN (Internet) |
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name-server: localhost.uoregon.edu. |
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email-address: hostmaster@uoregon.edu (the first dot is imputed as |
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being an @ sign) |
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serial-number: 2009120709 (common practice is to use a timestamp) |
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refresh: 7200 (time between slaves refreshing from the master |
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name server in seconds) |
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retry: 900 (time between retries if the slave fails to |
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connect with the master when refreshing, in seconds) |
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expiry: 605000 (time in seconds til a secondary copy of the |
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data from the master is no longer valid |
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) neg-cache-time: 86400 (time in seconds that a NEGATIVE (NXDOMAIN) |
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answer should be cached) |
In the typical model of a master server on campus and slaves both on and off-site, a failure that results in a loss of campus connectivity will cause several immediate effects:
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