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

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Root
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
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microsoft
DNS Servers
DNS Server
Root (.) Servers
com
Client
Root Hints
 !"#$%

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':'797+*+'+'?#/
microsoft.com

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4

Local DNS Server
Client Server
 !"#$%

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^7+I?@4<7&G'h#79':/
Where’s
ServerA?
ServerA is at
192.168.8.44
Where’s
ServerA?
ServerA is at
192.168.8.44
Client1
Client2
ServerA
DNS server cache
Host name IP address TTL
ServerA.microsoft.com 192.168.8.44 28 seconds
 !"#$%

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7+&+'+'/
SOA query for a zone
SOA query answered
IXFR or AXFR query for a zone

3
3
4
4
Resource record is
updated
SOA serial number is
updated
 !"#$%

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