How to test the primary DNS and backup DNS of a windows Host

I. Overview:

When listening to the course of yeslab QIN Ke's SecV3 SNF (ASA), the windows host will send a DNS request to the primary DNS and the standby DNS at the same time, so the building environment is ready for verification.

Ii. Basic test ideas and conclusions:

A. Basic Ideas:

① Configure primary DNS and backup DNS in the operating system

② When both the primary and backup DNS are available, issue a DNS query and capture packets

③ Manually stop the main DNS service and do not provide DNS queries. The PC sends DNS queries and captures packets.

④ Stop the primary DNS interface directly, send DNS queries on the PC, and capture packets

B. test conclusion:

① As a DNS client, the PC does not send queries to the primary DNS and the standby DNS at the same time. ② the DNS Client Always sends queries to the primary DNS first, the secondary DNS is available only when the primary DNS is unavailable.

Iii. Test topology:

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4. Basic Configuration:

A. PC:

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B. R1:Interface FastEthernet0/0
Ip address 10.1.1.1 255.255.255.0
No shutip dns server
Ip host www.baidu.com 10.1.1.1
C. R2:Interface FastEthernet0/0
Ip address 10.1.1.2 255.255.255.0
No shutip dns server
Ip host www.baidu.com 10.1.1.2 5. Test procedure:
A. Both R1 and R2 serve as DNS servers and can provide DNS queries. The PC sends DNS queries:650) this. width = 650; "src =" http://www.bkjia.com/uploads/allimg/131227/0935062643-2.jpg "title =" 1.JPG" alt = "225103232.jpg"/>
--- From packet capture, we can see that when the main DNS is available, only the query package for the main DNS server is issued. B. R1 and R2 serve as DNS servers. Only R2 can provide DNS query records, and the PC sends DNS queries:R1 (config) # no ip host www.baidu.com 10.1.1.1650) this. width = 650; "src =" http://www.bkjia.com/uploads/allimg/131227/0935061592-3.jpg "title =" 2.JPG" alt = "225213279.jpg"/> --- capture packets, we can see that when the primary DNS cannot be queried, will find the backup DNS.
C. Only R2 is a real DNS server and can provide DNS queries. The PC sends DNS queries:R1 (config) # no ip dns server650) this. width = 650; "src =" http://www.bkjia.com/uploads/allimg/131227/09350A450-4.jpg "title =" 3.JPG" alt = "225521250.jpg"/> --- From packet capture we can see that when the primary DNS cannot provide DNS services, you will also find the backup DNS. D. the IP address of the primary DNS is a nonexistent IP address. The secondary DNS can provide services and the PC sends DNS queries: R1 (config) # int f0/0

R1 (config-if) # shutdown

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--- From packet capture, we can see that when an arp request is sent to the primary server and no response is received, we will also find the backup DNS.

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