Difference between revisions of "Testing the DNS Name Resolution"

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Active Directory (AD) uses SRV records to locate services, such as Kerberos and LDAP. To verify that SRV records are resolved correctly, use the <code>nslookup</code> interactive shell:
 
Active Directory (AD) uses SRV records to locate services, such as Kerberos and LDAP. To verify that SRV records are resolved correctly, use the <code>nslookup</code> interactive shell:
   
# nslookup
+
$ nslookup
Default Server: 10.99.0.1
 
Address: 10.99.0.1
 
 
 
> set type=SRV
 
> set type=SRV
> _ldap._tcp.samdom.example.com.
+
> _ldap._tcp.samdom.example.com
Server: UnKnown
+
Server: 192.168.0.4
Address: 10.99.0.1
+
Address: 192.168.0.4#53
 
 
_ldap._tcp.samdom.example.com SRV service location:
+
_ldap._tcp.samdom.example.com service = 0 100 389 dc2.samdom.example.com.
 
_ldap._tcp.samdom.example.com service = 0 100 389 dc1.samdom.example.com.
priority = 0
 
  +
> exit
weight = 100
 
  +
port = 389
 
  +
Alternatively, you can use the host command.
svr hostname = dc1.samdom.example.com
 
  +
samdom.example.com nameserver = dc1.samdom.example.com
 
  +
$ host -t SRV _ldap._tcp.samdom.example.com
dc1.samdom.example.com internet address = 10.99.0.1
 
  +
_ldap._tcp.samdom.example.com has SRV record 0 100 389 dc1.samdom.example.com.
  +
_ldap._tcp.samdom.example.com has SRV record 0 100 389 dc2.samdom.example.com.
   
   

Latest revision as of 07:51, 9 October 2021

Introduction

To verify that your DNS settings are correct and your client or server is able to resolve IP addresses and host names use the nslookup command. The command is available on Linux and Windows.



Forward Lookup

To resolve a host name its IP address:

# nslookup DC1.samdom.example.com
Server:         10.99.0.1
Address:        10.99.0.1#53

Name:   DC1.samdom.example.com
Address: 10.99.0.1



Reverse Lookup

To resolve a IP address to its host name:

# nslookup 10.99.0.1
Server:        10.99.0.1
Address:	10.99.0.1#53

1.0.99.10.in-addr.arpa	name = DC1.samdom.example.com.

Note that in a Samba AD, the reverse zone is not automatically configured. To set up a reverse zone, see DNS Administration.



Resolving SRV Records

Active Directory (AD) uses SRV records to locate services, such as Kerberos and LDAP. To verify that SRV records are resolved correctly, use the nslookup interactive shell:

$ nslookup
> set type=SRV
> _ldap._tcp.samdom.example.com
Server:	192.168.0.4
Address:	192.168.0.4#53

_ldap._tcp.samdom.example.com	service = 0 100 389 dc2.samdom.example.com.
_ldap._tcp.samdom.example.com	service = 0 100 389 dc1.samdom.example.com.
> exit

Alternatively, you can use the host command.

$ host -t SRV _ldap._tcp.samdom.example.com
_ldap._tcp.samdom.example.com has SRV record 0 100 389 dc1.samdom.example.com.
_ldap._tcp.samdom.example.com has SRV record 0 100 389 dc2.samdom.example.com.



Error Messages

  • The DNS server is not able to resolve the host name:
** server can't find DC1.samdom.example.com: NXDOMAIN
  • The DNS server is not able to resolve the IP address:
** server can't find 1.0.99.10.in-addr.arpa: NXDOMAIN
  • The DNS server used is not available:
;; connection timed out; no servers could be reached