MacDNS FAQ's & Troubleshooting
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Troubleshooting Tips
Tips for Common
Symptoms
Symptom:
Others on the Internet are unable to resolve names
within the MacDNS domain.
- Attempt to resolve the name yourself
(possibly people reporting the problem have
their own problems or are using the wrong
names)
- Use the 'Whois' command
(http://rs.internic.net/cgi-bin/whois)
to make sure that the name is registered. The
record displayed will give the IP address of the
name server for the domain; verify that the IP
address given is that of the MacDNS server.
- Make sure that the MacDNS application is
running on the server and that the appropriate
zone file is open.
- Use the Lookup Host feature in MacDNS to
verify that the names have been set up
correctly.
- Use the Stats feature to capture to the log
information about IP addresses requests are
coming from; this will let you know whether or
not MacDNS is even receiving the request (see
below for more on
Stats).
- Verify the MacDNS server's Internet
connectivity by using a Web Browser, or other
type of IP application to connect to a host on
the Internet.
Symptom:
Hosts on the local LAN aren't able to resolve other
local names.
- Verify that the MacDNS application is
running on the server and that the appropriate
zone file is open.
- Use LookUp Host command in MacDNS to verify
proper configuration
- Check TCP/IP control panel or MacTCP control
panel of clients to confirm that they have the
MacDNS server listed as their first name server.
(See
configuring
clients)
- Check IP connectivity between the clients
and server with a ping utility or some other IP
application (using IP addresses instead of
domain names)
Symptom:
Hosts on the local LAN aren't able to resolve
non-local domain names.
- Verify the IP address of the parent name
server entered in the Zone Information window of
MacDNS; is it the correct IP address? is that
machine really a name server?
- Check the Cached Hosts window, to see if the
parent server did not respond, or responded
negatively (i.e., saying the host didn't exist).
(see Viewing the
cache, below) NOTE: Secondary
parent name servers will only be queried if no
response is received from the primary parent
server. If the primary parent server responds
that the host doesn't exist, that is a valid
response, and no further queries to the
secondary parent server will be made.
- Verify IP connectivity by pinging the parent
name server from the MacDNS server.
- Use MacDNS' Lookup Host command to send a
query to the parent name server.
- Verify the client configuration; the MacDNS
server should be listed as the first name
server.
- If making changes to the parent server, or
adding additional parent servers, be sure to
clear the hosts entry from the cache before
testing a second time.
Symptom:
Mail isn't being delivered to the mail server
- Use Lookup Host to verify that MacDNS is
successfully resolving names within its
domain.
- Verify that names within the MacDNS domain
can be resolved from people outside the LAN;
i.e., others on the Internet.
- Verify email address being used (i.e.,
teb@acme.com). Make sure both user portion (teb)
and host portion (acme.com) of the mail address
are correct.
- Check Mail Exchangers for host portion of
mail address being used. (Can use the Lookup
Host command in MacDNS for this.) In the mail
exchanger field, the host with the lowest
preference value should be the mail server.
- Verify the IP address of the mail server
host in MacDNS. Check what's listed in the
Permanent host field against what's listed in
the mail server's TCP/IP control panel.
- Verify that the mail server's permanent host
record has a mail exchanger pointing back to
itself, with the lowest preference number.
- Try sending mail from one client on the LAN
to another.
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Gathering
information
Viewing
the cache
Like other DNS servers,
MacDNS keeps a cache. Whenever MacDNS receives a
query for information that is not in its database,
it sends the query on to a parent server. Once
MacDNS receives information from the parent server,
it adds that information to its cache and responds
to the original requester. Subsequent queries for
the same information are then answered more
quickly.
TIP:
If troubleshooting problems resolving names, check
the Cached hosts window and clear the "No Response"
entry (if any) in the cached hosts window by
selecting it and choosing "Clear" from the Edit
menu. Otherwise, when you make further attempts to
resolve the name, MacDNS will only send you the
information stored in cache; what you really want
is for it to make another effort to resolve the
name by contacting the parent server(s). This is
especially important if you want to see what
changes occur after adding additional parent
servers, or change the IP address of the parent
server.
To view the cache:
/AppleShare IP 6.2 Install/Tutorials/MacDNS Tutorial/Media/cachedHosts2.gif/cachedHosts2.gif)
The cached query responses
are kept in a window that is similar to the host
list window, with the following
exceptions:
- Although double-clicking
will open an entry to view its current values
(such as TTL), no values can be changed (the OK
button is dimmed to prevent this).
- There are several
listings for Type:
- Cached entries
- the Negative entry,
which indicates that there is no such host
(and that the parent server has said so
authoritatively)
- the NoResp entry,
which indicates that MacDNS could not get a
response from any parent server for the
record.
Viewing
the Message Log
The MacDNS server keeps a
history of significant events that occur during its
operation. The information is displayed in the
Message Log window.
To view the Message Log:
- Choose Message Log from
the Window menu. The Message Log window appears.
Each entry in the Message Log indicates a date
and time and a text message.
/AppleShare IP 6.2 Install/Tutorials/MacDNS Tutorial/Media/MessageLog.gif/MessageLog.gif)
The log above shows that a
timeout is occurring when making an attempt to
resolve a name OUTSIDE of MacDNS server's domain
(log entries 11:22:03 to 11:22:36). After the
time out the first time, I added a second parent
server, and attempted the lookup again (after
removing the "No Resp" entry from Cached Hosts).
For the attempt that begins at 11:23:11, the
primary parent server is still tried first, but
when it times out, it tries the second parent
server, and the name is successfully resolved.
At the bottom of the
window is a pop-up menu that controls the level
of detail that appears in the Message Log
window, as shown in the following figure:
The levels of detail
are:
The MacDNS program creates a
log file that keeps the same information as
displayed in the Message Log window. The file is
created in the same folder as the MacDNS
program.
Viewing
server statistics
To view various statistics
gathered by the MacDNS program:
- Choose Show Query Counts
or choose Show Requesters from the Stats
menu.
- If you choose Show Query
Counts, a detailed summary of all queries
received by MacDNS is displayed in the Message
Log window.
- If you choose Show
Requesters, the IP addresses of all machines
that have requested information from MacDNS are
displayed in the Message Log window.
/AppleShare IP 6.2 Install/Tutorials/MacDNS Tutorial/Media/Stats.gif/Stats.gif)
- MacDNS
also gives you the option of trapping packets
into the Message Log. You can specify the number
of packets, and the IP address you want to trap
packets from (leaving this field blank will trap
packets from any IP address). This feature might
be of interest to the advanced network
administrator who knows how to interpret this
information. Assistance
with interpreting this data would be considered
beyond up and running support; the MacDNS
administrator's guide has further details on
it.
- The portion of the message log below shows
the type of information that is trapped.
/AppleShare IP 6.2 Install/Tutorials/MacDNS Tutorial/Media/trapped.gif/trapped.gif)
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