Chapter 8 – Troubleshooting DNS
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Reduces DNS look-up
traffic across an Internet connection or a WAN.
o
A DNS Server uses a
ÒforwarderÓ for requests only if they are records in certain domains. This is
useful for reducing WAN traffic when the authority for sub-domains is delegated
and each location has itÕs own Internet Connection.
o
Enable Round Robin
– occurs when more than one record exist for a DNS Query. The answer
returned for the query alternates between the records.
o
The Òsecure cache
against pollutionÓ option controls how the DNS server caches look-ups. In this
option, the DNS server does not cache look-up responses from
ÒNon-AuthoritativeÓ DNS Servers. This prevents hackers from placing false
information about other domains in your DNS cache.
o
Modifying EDNSO
– A new protocol, which allows DNS Servers to send UDP packets with more
than 512 bytes of information.
o
Servers that support
EDNSO send an ÒOPRTÓ record before DNS look-up requests. The OPRT record gives
the maximum size of DNS message that is supported by UDP
o
DNSLint – a
command line utility that allows you to verify corrent DNS configuration. Helps
to confirm that a zone is correctly configured or verify records.
o
Debug logging
– records packet-by-packet information about the queries that the DNS
server is receivig. Should be enabled only for troubleshooting because
it records a large volume of information.