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15.3 Using DNSLint
DNSLint, which we introduced back
in Chapter 8, can also come in handy when
you're troubleshooting. In Chapter 8, we mostly used it to verify the registration
of records by Domain Controllers. But DNSLint
can also come in handy in detecting delegation problems, as we showed
in Chapter 9.To use DNSLint to check delegation, use the
/d command-line option. Specify the domain name
of the zone whose delegation you'd like to check as
the argument. For example:
C:\> dnslint /d movie.edu
This produces a report on
movie.edu's delegation,
displayed in a browser window. If you're checking a
zone that's not registered on the
InterNIC's whois servers (i.e.,
a subdomain of com or net),
you'll also need to specify the
/s option and, as an argument, the IP address of
a name server authoritative for the zone.By default, DNSLint checks DNS over UDP. You can
instruct it to test DNS over TCP, too, using the
/test_tcp option.Finally, you can use the /c option to tell
DNSLint to check connectivity to the mail ports
(SMTP, POP, and IMAP, by default) on the mail servers it finds for
the zone. If you don't want it to check all three,
you can enumerate the protocols to check after the option; for
example:
C:\> dnslint /d movie.edu /c smtp,imap
Here's some sample DNSLint
output (in text format, generated using /t):
DNSLint Report
System Date: Sat Jul 05 18:58:05 2003
Command run:
dnslint /d fx.movie.edu /t /s 192.253.254.2 /c smtp
Domain name tested:
fx.movie.edu
DNS servers were identified as authoritative for the domain:
DNS server: bladerunner.fx.movie.edu
IP Address: 192.253.254.2
UDP port 53 responding to queries: YES
TCP port 53 responding to queries: Not tested
Answering authoritatively for domain: YES
SOA record data from server:
Authoritative name server: bladerunner.fx.movie.edu
Hostmaster: administrator.fx.movie.edu
Zone serial number: 10
Zone expires in: 1.00 day(s)
Refresh period: 900 seconds
Retry delay: 600 seconds
Default (minimum) TTL: 3600 seconds
Additional authoritative (NS) records from server:
outland.fx.movie.edu 192.253.254.3
bladerunner.fx.movie.edu 192.253.254.2
Mail Exchange (MX) records from server (preference/name/IP address):
100 wormhole.movie.edu 192.253.253.1
10 starwars.fx.movie.edu 192.253.254.4
DNS server: outland.fx.movie.edu
IP Address: 192.253.254.3
UDP port 53 responding to queries: YES
TCP port 53 responding to queries: Not tested
Answering authoritatively for domain: YES
SOA record data from server:
Authoritative name server: bladerunner.fx.movie.edu
Hostmaster: administrator.fx..movie.edu
Zone serial number: 10
Zone expires in: 1.00 day(s)
Refresh period: 900 seconds
Retry delay: 600 seconds
Default (minimum) TTL: 3600 seconds
Additional authoritative (NS) records from server:
outland.fx.movie.edu 192.253.254.3
bladerunner.fx.movie.edu 192.253.254.2
Mail Exchange (MX) records from server (preference/name/IP address):
10 starwars.fx.movie.edu 192.253.254.4
100 wormhole.movie.edu 192.253.253.1
Network Connectivity Tests
E-mail server: starwars.fx.movie.edu
IP address: 192.253.254.4
SMTP response: 220 starwars.fx.movie.edu ESMTP Postfix
POP response: Not Tested
IMAP response: Not Tested
E-mail server: wormhole.movie.edu
IP address: 192.253.253.1
SMTP response: 220 wormhole.movie.edu ESMTP Postfix
POP response: Not
Tested
IMAP response: Not Tested
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