nslookup vs dig for DNS troubleshooting on Network+

Try 3 questions on this

Pick an answer to see why each option is right or wrong.

1. A technician uses nslookup against a company name server and wants it answering only from data it holds, without querying other servers for the answer. Which of the following should be turned off?

   Right. In the game that’s Renown for your Network Troubleshooting building.

   Not that one: D is right. In the game your Network Troubleshooting building would lose a little Renown, and this question would come back later.

   Your answerA.CachingA cache stores answers the server has already fetched. Turning caching off would make the server fetch every answer again from other servers, the opposite of what the technician wants.Your answerB.Zone transfersZone transfers are how a secondary server copies a zone from the primary. They are not involved in answering a client's lookup, so disabling them changes nothing here.Your answerC.Reverse lookupsA reverse lookup asks for the name that belongs to an address. It is one kind of query, not a setting that controls whether the server asks other servers.The answerD.RecursionThe BIND nslookup manual says the recursion setting 'tells the name server to query other servers if it does not have the information', and 'the default is recurse'. Setting norecurse turns that off, so the server answers only from what it holds.

   Written from bind9.readthedocs.io/en/latest/manpages.html

2. A technician uses nslookup to query the MX type for a hostname that is valid but has only an A entry configured. Which of the following messages does nslookup return?

   Right. In the game that’s Renown for your Network Troubleshooting building.

   Not that one: B is right. In the game your Network Troubleshooting building would lose a little Renown, and this question would come back later.

   Your answerA.Nonexistent domainNonexistent domain is returned when 'the computer or DNS domain name doesn't exist'. The hostname here exists, it just has no data of the requested type.The answerB.No recordsThe nslookup reference lists 'No records' as: 'The DNS name server doesn't have resource records of the current query type for the computer, although the computer name is valid.' A valid name with an A record but no MX record produces exactly that.Your answerC.Timed outTimed out means the server 'didn't respond to a request after a certain amount of time and a certain number of retries'. The server is working and answered the query.Your answerD.No response from serverNo response from server means 'no DNS name server is running on the server computer'. That is a server problem, not a missing record type.

   Written from learn.microsoft.com/en-us/windows-server/administration/windows-commands/nslookup

3. A technician needs dig to show each name server in the delegation chain, starting at the root servers and ending at the one that answers. Which of the following options does this?

   Right. In the game that’s Renown for your Network Troubleshooting building.

   Not that one: C is right. In the game your Network Troubleshooting building would lose a little Renown, and this question would come back later.

   Your answerA.+shortThe +short option trims dig's output down to just the answer. It asks one server one question, as usual, and shows nothing of the path from the root.Your answerB.+tcpThe +tcp option changes the transport used for the query. It still sends a single query to a single server rather than walking down from the root.The answerC.+traceThe BIND dig manual says +trace toggles tracing of the delegation path from the root name servers for the name being looked up: dig makes iterative queries, follows referrals from the root servers and shows the answer from each server used to resolve the lookup.Your answerD.+norecurseThe +norecurse option asks the server to answer only from what it holds. dig still asks just that one server, so it does not show each step from the root down.

   Written from bind9.readthedocs.io/en/latest/manpages.html