(4) 4. A requesting host queries the DNS to learn the IP addross ost cached, whi

Question

(4) 4. A requesting host queries the DNS to learn the IP addross ost cached, which local name server's of a destination h Assuming the root DNS has the address of the intermediate naane server af the following query paths corresponds to the case where the queries are recursive and the root name server's queries are recursive root nane server rame saver al narc server 6 local name server-K=authoritaver 5 interm cdiate nme servex intormediste 5 name server tame requesting host detmationt questing host destination hoet ccal name authoritative name server local name server interm ediate name server nant server intennediate amc erver equeting host destination host Krequesing host xoot name server root mamo server (0 ocal name server authoritative mau server intemediate 6 hkme name server requeting host dotiationhot requesting host destination hot ) 5. Listed below is the DNS record for a fictitious company, Okoom. TTL (seconds) 60 86400 alue Name okcom.com okcom.com dns. okcom.com MX nail.okcom.com NS sleepy.okcom.com A 75. 175.211.47 86400 grumpy.okcom.comA happy. okcom.com A 75.175.211.73 75.175.211.98 75.175.211.62 86400 86400 86400 mail.okcom.con 86400 sleepy. okcom. com CHAME happy.okcom.com www.okcom,com CNAME grumpy.okcom.com 86400 According to this record, the IP address of the authoritative name server for the domain okcom.com is (a) 75.175.211.47 (b) 75.176.211.73 c) 75.175.211.98 d) dne.okcom.com e) happy.okcom.com (f) sleepy.okcom.com

Explanation / Answer

4) Option C is the correct choice.

     In DNS if any server is recursive then if a request came to this

     recursive server then it will serve the request without giving

     address of anathor server who will resolve the request.

     Here given both local name server and root name server are recursive.

     1) Now at 1st the request from host will go to local name server

     2) Here local name server main task is that it has to serve the request of host,

         and hence local name server request root name server.

     Here root server is recursive and hence it cant give any address of

     anathor server to local name server , root server has to resolve the

     query of local name server.

     3) Hence root name server queries intermediate name server

     4) After it got the response from intermediate name server

     5) Root name server queries authorative name server.

     6) Now the response came from authorative name server to root name server.

     7) Root name server will give the response to local name server.

     8) Finally local name server give the response to the host

   Hence Option C is the correct choice.

5)

      Authoritative name server details will be available in record type is NS (Name server).

      Here okcom.com NS record contains sleepy.okcom.com

      Now sleepy.okcom.com CNAME is happy.okcom.com

      Now happy.okcom.com IP address is 75.175.211.98

      Hence the answer is 75.175.211.98.

   

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