This question
should be used to assess the skills of a Network Administrator
with one or two years of experience. This question will
determine if the candidate has had some practical experience
with DNS and if he or she understands the different zone
files and their relationship.
A
new entry has been made in the DNS tables for a machine.
When you ping the machine,"Newguy.ourhome.com" you get this
response:
Ping newguy.ourhome.com
Pinging
newguy.ourhome.com [192.168.2.5] with 32 bytes of data:
Reply
from 192.168.2.5: bytes=32 time=50ms TTL=238
Reply from 192.168.2.5: bytes=32 time=41ms TTL=238
Reply from 192.168.2.5: bytes=32 time=40ms TTL=238
Reply from 192.168.2.5: bytes=32 time=40ms TTL=238
Ping
statistics for 192.168.2.5:
Packets: Sent = 4, Received = 4, Lost = 0 (0%
loss),
Approximate round trip times in milli-seconds:
Minimum = 40ms, Maximum = 50ms, Average = 42ms
But
when you try a reverse lookup - "Ping -a 192.168.2.5" -
you get a reply that starts out like this:
Pinging
newguy.ourhome.com.2.168.192.in.addr.arpa
What
has gone wrong?
(a)
Your zone file is missing
(b) Your FQDN is a duplicate
(c) Your "PTR" record is incorrect
(d) You're "A" record is incorrect
The
correct answer is C. Extra points for the candidate if he
or she can tell you the cause is a missing trailing dot
at the end of the new PTR record.
Answer A is incorrect
since there would be much larger DNS issues if zone files
were missing.
Answer B is incorrect
since duplicate names on the network can cause conflicts
on the network but do not cause this problem.
Answer D is incorrect
since mistakes in an "A" record would affect the forward
file entries not the reverse as is the case with this error.
About the author
Kate Stevely is a Technical Infrastructure Specialist and
has been in the IT field for nearly 20 years. This has included
work with mainframes, distributed platforms, most flavors
of Unix and Windows. Main areas of interest are Networking,
Storage, Backup and Recovery, and Business Continuity.
