Testing the DNS Name Resolution: Difference between revisions

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<noinclude>
On Windows and *nix, you can use „nslookup“ to test if your computer can resolve records by using your DNS. Try resolving the name of your Domain Controller into its IP:
= Introduction =
</noinclude>

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

== Forward Lookup ==

To resolve a host name its IP address:


# nslookup DC1.samdom.example.com
# nslookup DC1.samdom.example.com
Server: 192.168.1.1
Server: 10.99.0.1
Address: 192.168.1.1#53
Address: 10.99.0.1#53
Name: DC1.samdom.example.com
Name: DC1.samdom.example.com
Address: 192.168.1.1
Address: 10.99.0.1


alternatively you can use the <code>host</code> command:
Nslookup will show you, which server was asked (192.168.1.1) and the result of your query (DC1.samdom.example.com has IP 192.168.1.1)


# host DC1.samdom.example.com
To query a SVR record, you have to start nslookup and set the type to „SRV“, to retrieve the values (works on Windows and *nix):
DC1.samdom.example.com has address 10.99.0.1


== Reverse Lookup ==
# nslookup

Default Server: UnKnown
To resolve a IP address to its host name:
Address: 192.168.1.1

# 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.

or

# host 10.99.0.1
1.0.99.10.in-addr.arpa domain name pointer 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|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 <code>nslookup</code> interactive shell:

$ nslookup
> set type=SRV
> set type=SRV
> _ldap._tcp.samdom.example.com.
> _ldap._tcp.samdom.example.com
Server: UnKnown
Server: 192.168.0.4
Address: 192.168.1.1
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
svr hostname = dc1.samdom.example.com
samdom.example.com nameserver = dc1.samdom.example.com
dc1.samdom.example.com internet address = 192.168.1.1


or
If your query can't be answered, because it doesn't exist, you'll receive

$ 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
** server can't find DC1.samdom.example.com: NXDOMAIN


* The DNS server is not able to resolve the IP address:
If you query a none existing DNS server, it would result in

** 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
;; connection timed out; no servers could be reached

Latest revision as of 12:11, 6 March 2022

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 or host commands. The nslookup 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

alternatively you can use the host command:

# host DC1.samdom.example.com
DC1.samdom.example.com has 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.

or

# host 10.99.0.1
1.0.99.10.in-addr.arpa domain name pointer 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

or

$ 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