In concept, testing DNS/BIND servers consists
of locating the information you need.
In practice, testing DNS servers involves
tracing through a network of servers and their databases to find the server
responsible for the information.
This chapter describes the tests you can
use to locate the information.
11.1 Glossary
The following terms are used in this section. Refer to them as needed during the problem solving tests.
A server that stores information locally. Master and slave servers are examples of authoritative servers. They have primary and secondary authority, respectively, for a given domain.
In contrast, a server that is not authoritative must ask other servers for information about the target host. A forward-only server is an example of this type of server because it forwards queries to a list of forwarders that can answer such requests.
The server you are currently logged in to and running tests from.
The types of resource records in the DNS database
files.
See
named(8)
A server
that can answer DNS queries from data in its databases and cache, whether
or not it is authoritative for the information.
Forwarder entries can be
in the
named.conf
file.
Nameserver records map a domain name to a system that serves the domain, and determine whether a system is familiar with the name servers for the authoritative domain. Nameserver records have the following form:
domain-name IN NS machine-name
On the left is the domain name; on the right is the name of the machine that services the domain.
A server that stores the main copy of a target domain's databases. A master server has primary authority for name service information in a given domain.
A server that pulls a copy of the target domain's data from another server. In most cases, the data is pulled from a master server. However, in some cases, the data is pulled from another slave server.
A slave server has secondary authority for name service information in a given domain.
Start of authority records mark the start of a zone of authority. They occur at the beginning of each master database file. SOA records have the following form:
domain-name IN SOA machine-name
The portion of the target host name that begins after the first period (.).
The host name you are trying to resolve. The target domain name is derived from the target host name.
Figure 11-1
shows the DNS Server Testing Worksheet,
which you can use to record information from the tests in the following sections.
If you are viewing this manual online, you can use the print feature of your
browser to print a copy of this worksheet.
On a copy of the worksheet, write
the current server's name, current domain name, and target domain name.
Figure 11-1: DNS Server Testing Worksheet
11.3 Starting the DNS Server Test
To determine if the current server can resolve the target data, complete the following steps:
Determine whether the current server can access the target data. Use the following commands:
# nslookup Default Server: host1.corp.com Address: 127.0.0.1 > server localhost Default Server: localhost.corp.com Address: 127.0.0.1 > set timeout=45 > set retry=2 > target_host.target_domain.
If the
nslookup
command: |
Action: |
| Succeeds | Go to step 3. |
| Fails | If the first time, go to step 2. |
| If the second time, go to Section 11.4. |
Determine whether the
named
daemon is running
by using the following command:
# ps gax | grep named
If the
named
daemon is: |
Action: |
| Running | Go to step 1. |
| Not running | Start the daemon by using the
/sbin/init.d/named
start
command.
If the Internet name service started message is displayed,
go to step 1. |
| If the message is not displayed, this machine is not configured as a DNS server. Decide how the machine is to be configured. See Section 2.5 for more information. |
Log in to the client system and use the
nslookup
command to try to access the target data.
If the
nslookup
command: |
Action: |
| Succeeds | STOP. The client can resolve the target data. |
| Fails | The server knows the information,
but is not transferring it to the client.
Log out from the client; restart
DNS on the server by using the
/sbin/init.d/named restart
command; log in to the client; and use the
nslookup
command.
If it cannot resolve the target data, you have the wrong server or the DNS
server is malfunctioning. |
11.4 Determining the Server Type
To determine whether the current server is a master server or a slave server, complete the following steps:
Compare the target domain name with all domain names of the
master and slave entries in the
/etc/named.conf
file.
These
entries have the following form:
zone "domain" {type server-type;file "filename.db";};
The following example shows the zz.bb.cc. target domain and subsets of this target domain:
# cat /etc/named.conf
.
.
.
options { directory "/etc/namedb"; }; zone "aa.bb.cc" { [1] type master; file "aa.bb.cc.db"; }; zone "cc" { [2] type master; file "cc.db"; }; zone "bb.cc" { [3] type slave; file "bb.cc.db"; masters { 128.102.0.42; }; }; zone "zz.bb.cc" { [4] type slave; file "zz.bb.cc.db"; masters { 128.102.29.73; }; };
.
.
.
This zone entry is not a subset of the zz.bb.cc. domain. [Return to example]
This zone entry is a subset of the zz.bb.cc.
domain.
The server
is a master server for the cc.
domain and it stores the information for this
domain in the
cc.db
file.
[Return to example]
This zone entry is a subset of the zz.bb.cc.
domain.
The server
is a slave server for the bb.cc.
domain and it stores the information for
this domain in the
bb.cc.db
file.
[Return to example]
This zone entry matches the zz.bb.cc.
domain.
The server is
a slave server for the zz.bb.cc.
domain and it stores the information for
this domain in the
zz.bb.cc.db
file.
[Return to example]
For more information on the format of the
named.conf
file, see
named.conf(8)
When directed, record information in the
named.conf
file section on the worksheet.
If a
named.conf
entry: |
And the type is: | Action: |
| Matches the target domain name | Master | Write the server type, domain name, and database file name on the worksheet and go to Section 11.8. |
| Slave | Write the server type, domain name, database file name, and host IP addresses on the worksheet and go to Section 11.7. | |
| Is a subset of the target domain name | Master | Write the server type, domain name, and database file name on the worksheet and go to step 2. |
| Slave | Write the server type, domain name, database file name, and host IP addresses on the worksheet and go to step 2. | |
| Neither matches nor is a subset of the target domain name | Master or slave | Go to Section 11.5. |
Compare the target domain name with all nameserver (NS) records in the database file recorded on the worksheet. When directed, record information in the Nameservers section on the worksheet. Use the following commands to create and view a list of NS records:
# grep -n NS database_file > ns_list # grep -n ORIGIN database_file >> ns_list # sort -n ns_list > ns_list.srt # cat ns_list.srt
The following example shows the file created by these commands. The target domain is zz.bb.cc.:
# cat ns_list.srt 1:$ORIGIN cc. 10: IN NS server_1.cc. 17:$ORIGIN cc. 18:bb IN NS server_3.bb.cc. 21:$ORIGIN cc. 22:bb IN NS server_4.bb.cc. 41:$ORIGIN bb.cc. 42:zz IN NS server_5.zz.bb.cc. [1] 45:$ORIGIN bb.cc. 46:zz IN NS server_6.bb.cc. [2]
This entry is a longer subset (exact match) of the target domain. The domain name from the preceding $ORIGIN line, .bb.cc., is appended to the domain name of this line, zz, resulting in zz.bb.cc.. [Return to example]
This entry is a longer subset (exact match) of the target domain. The domain name from the preceding $ORIGIN line, .bb.cc., is appended to the domain name of this line zz, resulting in zz.bb.cc.. [Return to example]
If any
NS
record: |
And the server is: | Action: |
| Contains a longer subset of the target domain name than the domain name on the worksheet | Master or slave | The server has neither primary nor secondary authority for the target information. Write the names of the servers on the worksheet and go to step 3. |
| Does not contain a longer subset of the target domain name than the domain name on the worksheet | Master | The database files contain the target information. Go to Section 11.8. |
| Slave | The database files contain the target information. Go to Section 11.7. |
Find the IP addresses in the database file for any name servers on the worksheet. Use the following commands:
# grep -n ORIGIN database_file > ip_list # grep -n server_name database_file >> ip_list
.
.
.
# sort -n ip_list > ip_list.srt # cat ip_list.srt
Write the IP addresses on the worksheet next to the corresponding server name and go to Section 11.5. The following example shows the file created by the preceding commands:
# cat ip_list.srt 1:$ORIGIN cc. 17:$ORIGIN cc. 21:$ORIGIN cc. 41:$ORIGIN bb.cc. 42:zz IN NS server_5.zz.bb.cc. 43:$ORIGIN zz.bb.cc. 44:server_5 IN A 10.140.48.3 [1] 45:$ORIGIN bb.cc. 46:zz IN NS server_6.bb.cc. 47:$ORIGIN bb.cc. 48:server_6 IN A 10.12.48.3 [2]
The IP address for server_5 is 10.140.48.3. [Return to example]
The IP address for server_6 is 10.12.48.3. [Return to example]
11.5 Finding the Target Domain Information
To determine the servers that the current server communicates with in order to get information for the target domain, complete the following steps:
Search the
named.conf
file and find any
forwarder entries.
These entries have the following form:
options { directory "directory-name"; forward only; forwarders { IP-address; IP-address; }; };
When directed, record information in the Forwarders section on the worksheet.
| If your system: | Action: |
| Contains a forwarder line | The current server forwards requests. Write the IP addresses for any forwarders on the worksheet and go to Section 11.6. |
| Does not contain a forwarder line | The current server does not forward queries. Go to step 2. |
Compare the target domain name with all nameserver (NS) records in the database file recorded on the worksheet. When directed, record information in the Nameserver section on the worksheet.
Use the following commands to create and view a list of NS records for each database file:
# grep -n NS database_file > ns_list # grep -n ORIGIN database_file >> ns_list # sort -n ns_list > ns_list.srt # cat ns_list.srt
| If any NS record: | And: | Action: |
| Contains a longer subset of the target domain name than the domain name on the worksheet | -> | Write the names of the servers on the worksheet and go to step 3. |
| Does not contain a longer subset of the target domain name than the domain name on the worksheet | The Nameserver section on the worksheet is blank | Go to Section 11.9. |
Find the IP addresses in the database file for any name servers on the worksheet. Use the following commands:
# grep -n ORIGIN database_file > ip_list # grep -n server_name database_file >> ip_list
.
.
.
# sort -n ip_list > ip_list.srt # cat ip_list.srt
Write the IP addresses on the worksheet next to the corresponding server name and go to step 4.
Verify whether each server listed in the Nameserver section
on the worksheet is reachable by using the
ping
command.
| If a server: | And: | Action: |
Responds to the
ping
command |
You have root access to the server | The server is reachable and under your administrative control. Note both items on the worksheet. Go to step 5. |
| You do not have root access to the server | The server is reachable, but not under your administrative control. Note both items on the worksheet. Go to step 5. | |
Does not respond to the
ping
command |
-> | Note this on the worksheet. |
If no servers responded to
the
ping
command, STOP.
The current server is isolated
from its servers on the network.
You cannot solve the problem; contact your
enterprise network administrator. |
Log in to each reachable server by using the
telnet
command.
Each server you log in to becomes the current server.
Get a new worksheet and write the current server name, current domain name,
and target domain name on it.
For each server, perform the DNS server test.
See
Section 11.3.
To determine whether the forwarders prevent you from resolving the target host name, complete the following steps:
Determine whether each forwarder listed on the worksheet is
reachable by using the
ping
command.
| If a forwarder: | And: | Action: |
Responds to the
ping
command |
You have root access to the forwarder | The forwarder is reachable and under your administrative control. Note both items on the worksheet. Go to step 2. |
| You do not have root access to the forwarder | The forwarder is reachable, but not under your administrative control. Note both items on the worksheet. Go to step 2. | |
Does not respond to the
ping
command |
-> | Note this on the worksheet. |
If no forwarders responded
to the
ping
command, STOP.
The current server is isolated
from its forwarders on the network.
You cannot solve the problem; contact
your enterprise network administrator. |
Edit the
named.conf
file and eliminate
any forwarders that did not respond to the
ping
command.
Enter the
nslookup
command again for the
target host.
If the
nslookup
command: |
Action: |
| Succeeds | Go to step 4. |
| Fails | Go to step 5. |
Edit the
named.conf
file and add the forwarders
removed in step 2 at the end of the forwarders line.
In addition, contact
the administrators of forwarders not under your administrative control and
inform them that they might have a problem with their forwarder.
STOP.
Log in to each reachable forwarder by using the
telnet
command.
This forwarder is now the current server.
On a new
worksheet, write the current server name, current domain name, and target
domain name.
For each server, perform the DNS server test.
See
Section 11.3.
| If the forwarder or other machines: | Action: |
| Cannot resolve the target name | Remove the forwarder from
named.conf
file. |
| Can resolve the target name | STOP. |
To determine whether the slave server contains the target data, complete the following steps:
Find the database serial number in the start of authority record in the database file. Use the following command:
# head -4 database_file
Write
the first number, which is the serial number, on the worksheet in the
named.conf
section.
If you have a serial number on a previous worksheet,
compare the current serial number with that one.
Note whether the current
number is larger (newer) or smaller (older) than the other number.
In the
following example, 23 is the serial number:
# head -4 database_file
$ORIGIN cc.
bb IN SOA host1.bb.cc. postmaster.host1.bb.cc. (
23 300 60 1209600 43200 )
IN MX 100 host1.bb.cc.
Determine whether the target data is contained in the database file written on the worksheet. Use the following commands to create and view a list of resource records:
# grep -n data_type database_file > ns_list # grep -n ORIGIN database_file >> ns_list # sort -n ns_list > ns_list.srt # cat ns_list.srt
| If the database file: | And the serial number is: | Action: |
| Contains the target data | Newer | The data exists in the domain. Go to step 3. |
| Contains the target data | Older or same | The server is malfunctioning or you made a error. Verify all steps up to this point. |
| Does not contain the target data | -> | The data does not exist in the domain. Go to step 4. |
Determine whether the current server can access the target data. Use the following commands:
# nslookup Default Server: host1.corp.com Address: 127.0.0.1 > server localhost Default Server: localhost.corp.com Address: 127.0.0.1 > set timeout=45 > set retry=2 > target_host.target_domain.
If the
nslookup
command: |
And the database serial number is: | Action: |
| Succeeds | -> | STOP. The server is working. Either the client or server cannot communicate with the server or this server just started working. |
| Succeeds | Newer | Log out of the slave server. Get the previous slave server's worksheet and go to step 8. |
| Fails | -> | Restart the current slave server by using
the
/sbin/init.d/named
restart command.
Then reenter the
nslookup
command. |
Verify whether each name server listed on the worksheet is
reachable by using the
ping
command.
| If a server: | And: | Action: |
Responds to the
ping
command |
You have root access to the server | The server is reachable and under your administrative control. Note both items on the worksheet. |
| You do not have root access to the server | The server is reachable, but not under your administrative control. Note both items on the worksheet. | |
Does not respond to the
ping
command |
-> | Note this on the worksheet. |
If no servers responded to
the
ping
command, STOP.
The current server is isolated
from its servers on the network.
You cannot solve the problem; contact your
enterprise network administrator. |
Count the number of servers that responded to the
ping
command and that are under your administrative control.
If the number is zero
(0), go to
Section 11.10.
Edit the
named.conf
file and find the
slave
entry.
Delete the IP address for those servers that are not
reachable and are not under your administrative control.
Delete those entries
from the worksheet as well.
Log in to each reachable server by using the
telnet
command.
Start a new worksheet for each server, writing the server
name as the current server.
Save the old worksheet.
Compare the target domain name with all domain names of the
master and slave entries in the
/etc/named.conf
file.
These
entries have the following form:
zone "domain" {type server-type;file "filename.db";};
When directed, record information in the
named.conf
file section on the worksheet.
If a
named.conf
entry: |
And the first field is: | Action: |
| Matches the target domain name | Master | Write the domain name and database file name on the worksheet and go to Section 11.8. |
| Slave | Write the domain name, host IP addresses, and the database file name on the worksheet and go to step 1. | |
| Is a subset of the target domain name | -> | STOP. Examine another master or slave server entry. |
| Neither matches nor is a subset of the target domain name | -> | STOP. Examine the next master or slave server entry. |
Restart the current slave server by using the following command:
# /sbin/init.d/named restart
After restarting, wait a few minutes before proceeding to the next step. This allows time for the database to be updated.
Determine whether the current server can access the target data. Use the following commands:
# nslookup Default Server: host1.corp.com Address: 127.0.0.1 > server localhost Default Server: localhost.corp.com Address: 127.0.0.1 > set timeout=45 > set retry=2 > target_host.target_domain.
If the
nslookup
command: |
Action: |
| Succeeds | STOP.
The server is working.
If you are in
a
telnet
session to another slave server, log out and go
to step 8.
|
| Fails | If you just ended a
telnet
session to another server, go to step 10. |
If you did not end a
telnet
session, either the current server is malfunctioning and
cannot read the database file or you made an error.
Verify all steps up to
this point. |
Compare the database serial number of the current server with the database serial number of the server from which you just logged out. Use the following command:
# head -4 database_file
| If the current database serial number is: | Action: |
| Older | Either the server cannot pull the database from the authoritative server or you made an error. Verify all steps up to this point. |
| The same | The serial numbers cannot be equal. Verify all steps up to this point. |
To determine whether the master server contains the target data, complete the following steps:
If you are in a
telnet
session from a slave
server to a master server, go to step 2.
Otherwise, go to step 3.
Find the database serial number in the start of authority record in the database file. Use the following command:
# head -4 database_file
Write
the first number, which is the serial number, on the worksheet in the
named.conf
section.
If you have a serial number on a previous worksheet,
compare the current serial number with that one.
Note whether the current
number is larger (newer) or smaller (older) than the other number.
In the
following example, 23 is the serial number:
# head -4 database_file
$ORIGIN cc.
bb IN SOA host1.bb.cc. postmaster.host1.bb.cc. (
23 300 60 1209600 43200 )
IN MX 100 host1.bb.cc.
Determine whether the target data is contained in the database file written on the worksheet. Use the following commands to create and view a list of resource records:
# grep -n data_type database_file > ns_list # grep -n ORIGIN database_file >> ns_list # sort -n ns_list > ns_list.srt # cat ns_list.srt
| If the database file: | Action: |
| Contains the target data | The data exists in the domain. Go to step 4. |
| Does not contain the target data | The data does not exist in the domain. Go to step 5. |
Determine whether the current server can access the target data. Use the following commands:
# nslookup Default Server: host1.corp.com Address: 127.0.0.1 > server localhost Default Server: localhost.corp.com Address: 127.0.0.1 > set timeout=45 > set retry=2 > target_host.target_domain.
If the
nslookup
command: |
And the database serial number is: | Action: |
| Succeeds | -> | STOP. The server is working. Either the last server cannot communicate with this server or this server just started working. |
| Succeeds | Older or same | STOP. The server is malfunctioning or you made an error. Verify all steps up to this point. |
| Succeeds | Newer | Log out of the master server. Get the previous slave server's worksheet and go to step 8 in Section 11.7. |
| Fails | -> | Restart the current master server by using
the
/sbin/init.d/named restart
command.
Then reenter the
nslookup
command. |
Edit the database file and increment the database serial number by 1 to age the database. The following example shows the SOA record before and after editing. Note the serial number increase from 23 to 24.
# head -4 database_file
$ORIGIN cc.
bb IN SOA host1.bb.cc. postmaster.host1.bb.cc. (
23 300 60 1209600 43200 )
IN MX 100 host1.bb.cc.
# vi database_file
.
.
.
# head -4 database_file
$ORIGIN cc.
bb IN SOA host1.bb.cc. postmaster.host1.bb.cc. (
24 300 60 1209600 43200 )
IN MX 100 host1.bb.cc.
Edit the database file and add new data to the database.
Refer
to
Section 11.1
for information on valid data types.
Precede
any new entry with a
$ORIGIN
entry, and separate database
fields with a tab character.
The following example shows a new address record
for host host1.bb.cc.:
$ORIGIN bb.cc host1 IN A 16.141.112.11
Restart the master server by using the following command:
# /sbin/init.d/named restart
Determine whether the current server can access the target data. Use the following commands:
# nslookup Default Server: host1.corp.com Address: 127.0.0.1 > server localhost Default Server: localhost.corp.com Address: 127.0.0.1 > set timeout=45 > set retry=2 > target_host.target_domain.
If the
nslookup
command: |
Action: |
| Succeeds | Log out of the master server. Get the previous slave server's worksheet and go to step 8 in Section 11.7. |
| Fails | Either the server is malfunctioning or you made an error. Verify all steps up to this point. |
11.9 Tracing Information from the Root Name Server
To resolve the target name beginning with the root of the DNS namespace, complete the following steps:
Determine whether the current server has a cache file containing the information necessary to find a root server. Use the following command:
# grep cache /etc/named.conf
| If a cache line: | Action: |
| Does not exist | The current server cannot contact a root name server. Note this on the worksheet and go to step 2. |
| Exists | Note this on the worksheet and go to step 3. |
Add a cache file to your server.
Caution
Adding a cache file alters many system files. Perform the following steps as shown to ensure the correct operation of your system.
Create copies of specific DNS and system files. Enter the following commands:
# cd /etc # cp -r namedb namedb.back # cp rc.config.common rc.config.common.back # cp hosts hosts.back # cp resolv.conf resolv.conf.back # cp svc.conf svc.conf.back # cd /var/adm/sendmail # cp sendmail.cf sendmail.cf.back
Display the name of the local host by using the
hostname
command.
You will need to reset the host name after running
the SysMan Menu utility and copying system files.
Run the SysMan Menu utility.
Modify the configuration
and create a caching server (see
Section 2.5.3).
Do not start
the DNS daemon automatically and do not run
svcsetup.
Copy the system files to the
/etc
directory.
Use the following commands:
# cd /etc # cp rc.config.common.back rc.config.common # cp hosts.back hosts # cp resolv.conf.back resolv.conf # cp svc.conf.back svc.conf
Set the host name to the original host name by using the
hostname
command.
Copy the
sendmail
file to the
/var/adm/sendmail
directory and restart
sendmail.
Use the following commands:
# cd /var/adm/sendmail # cp sendmail.cf.back sendmail.cf # /sbin/init.d/sendmail restart
Copy the DNS files to the
/etc
directory.
Use the following commands:
# cd /etc # cp namedb/namedb.boot namedb.back/named.conf_new # cp namedb/namedb.ca namedb.back # rm -rf namedb.back namedb # mv namedb.back namedb # cd namedb
Edit the
named.conf
file and add the following
lines to the end of the file:
zone "." {
type hint;
file "named.ca";
};
Remove the
named.conf_new
file.
Restart the current server by using the
/sbin/init.d/named restart
command.
Display the
named.ca
file by using the
following command:
# cat named.ca
Write the root name server names and IP addresses in the Root nameservers section on the worksheet.
Verify whether each root name server listed on the worksheet
is reachable by using the
ping
command.
| If a root name server: | Action: |
Responds to the
ping
command |
Note this on the worksheet. Go to Section 11.11. |
Does not respond to the
ping
command |
Note this on the worksheet.
If no servers
responded to the
ping
command, go to step 5. |
Do either of the following:
Give the current server access to the Internet.
Then restart
the
named
daemon by using the following command:
# /sbin/init.d/named restart
Keep the current server and worksheet, and go to Section 11.3.
Add a forwarder entry to direct the current server to communicate
with a machine with Internet access.
Then restart the
named
daemon by using the following command:
# /sbin/init.d/named restart
Keep the current server and worksheet, and go to Section 11.3.
To resolve target data using a name server, complete the following steps:
Enter the
nslookup
command for the target
system.
Choose the first name server from either the Root nameserver section
or the Nameserver section.
Use the following commands:
current_server> nslookup Default Server: localhost.omni.corp.com Address: 127.0.0.1 > server IP_address Default Server: [IP_address] Address: 128.102.16.10 > set type data_type > target_name
If the
nslookup
command: |
And: | Action: |
| Succeeds | -> | STOP. The server is working. Either the last server you tested does not talk to this one or this server just started working. Verify all steps completed up to this point. |
| Fails | An error message is returned. | If a
non-existent domain
message is displayed, no data exists for the
target_name.
Go to
Section 11.11. |
If a
no information
available
message is displayed, the
target_name
exists, but is not associated with the target data.
If the data is required,
contact the target domain administrator and request that the data be added
to the domain. |
||
If a
timed-out
message is displayed, the server to which you sent the query cannot contact
the server that is responsible for the target data.
Go to step 2. |
||
| Fails | An error message is not returned. | An unknown error. Contact the target domain administrator. |
Modify the retry and timeout values and re-enter the
nslookup
command.
Enter the following commands:
current_server> nslookup
Default Server: localhost.omni.corp.com
Address: 127.0.0.1
> server IP_address
Default Server: [IP_address]
Address: IP_address
> set type data_type
> target_name
If the
nslookup
command: |
And: | Action: |
| Succeeds | -> | STOP. The server is working, but is slow. This might prevent the query from being resolved. If the network connection to the server is correct, wait two or three hours for the performance to improve. If it does not improve, contact the server administrator. |
| Fails | An error message is returned | If a
non-existent domain
message is displayed, no data exists for the
target_name.
Go to
Section 11.11. |
If a
no information
available
message is displayed, the
target_name
exists, but the target data is not associated with it.
If the data is required,
contact the target domain administrator and request that the data be added
to the domain. |
||
If a
timed-out
message is displayed, the server to which you sent the query cannot access
the server that is responsible for the data.
Select another nameserver from
the worksheet and go to step 1. |
||
| Fails | An error message is not returned | An unknown error. Contact the target domain administrator. |
11.11 Finding the First Nonexistent Domain
To find the first nonexistent domain in a target name, complete the following steps:
Enter the
nslookup
command, using the smallest
subset of the target domain name.
Enter the following commands:
current_server> nslookup
Default Server: localhost.omni.corp.com
Address: 127.0.0.1
> server IP_address
Default Server: [IP_address]
Address: IP_address
> set type=ns
> target_name_subset
For example, if the target domain name is zz.bb.cc., the first attempt is to resolve the target name subset cc.. If necessary, the second attempt uses bb.cc., and the third, zz.bb.cc..
If the
nslookup
command: |
And: | Action: |
| Succeeds | -> | Go to step 3. |
| Fails | An error message is returned | If a
non-existent domain
message is displayed, no data exists for the
target_name.
If the data is required, contact the domain administrator and request that
the data be added to the domain.
STOP. |
If a
timed-out
message is displayed, go to step 2. |
Modify the retry and timeout values and enter the
nslookup
command again.
Enter the following commands:
current_server> nslookup
Default Server: localhost.omni.corp.com
Address: 127.0.0.1
> server IP_address
Default Server: [IP_address]
Address: IP_address
> set retry=2
> set timeout=45
> set type=ns
> target_name_subset
If the
nslookup
command: |
And: | Action: |
| Succeeds | -> | Go to step 3. |
| Fails | An error message is returned | If a
non-existent domain
message is displayed, no data exists for the
target_name.
If the data should exist, contact the domain administrator and request that
the data be added to the domain.
STOP. |
If a
timed-out
message is displayed, select another name server from the worksheet and go
to
Section 11.10. |
Add the next part of the target domain name to the target subset and go to step 1.