How to configure a DNS server

Owned by Kelli Higdon
Last updated: Mar 01, 2024
4 min read

 

Symptom

To create test SIP calls to a Dialogic IMG Integrated Media Gateway using a hostname rather than IP address, a local DNS server is required.

Reason for the issue:

IMG Gateways support SIP calls that use a FQDN (Fully Qualified Domain Name)

Note: The following procedure was tested on a Dialogic Gate Control Element Management System (GCEMS) server running Redhat ES 3.0

IMG Gateways run a DNS client that is configured to send a DNS request to the DNS server for SIP calls.

Configuring a static DNS server on Linux Red Hat ES3: 

1. Decide on a domain name.
         
2. Edit the /etc/resolv.conf file and add the loopback ip as the first entry in this file.

nameserver 127.0.0.1


3. Edit the /etc/named.conf file and add an entry for the domain, and an entry for each network configured on the server.
          
Domain: The zone name will be the domain name.
 

               zone "gcems_lf.com" { 
               type master;
               file "gcems_lf.com.zone";
               };


Network: Note that the IP address for the network is missing the last field and is in reverse order.
 

              zone "51.129.10.IN-ADDR.ARPA" { 
              allow-update { none; };
              type master;
              file "10.129.51.zone";
              };


         
4. In the /var/named folder create a file for each zone created in the named.conf file above.

Create /var/named/gcems_lf.com.zone.

The following example uses these values:
 
               Host name: lforsberg
               Domain name: gcems_lf.com

 Use this file to add static DNS entries.
 

[root@lforsberg named]# more gcems_lf.com.zone $TTL 86400 @ IN SOA lforsberg.gcems_lf.com root.lforsberg.gcems_lf.com ( 10 ; serial 28800 ; refresh 14400 ; retry 3600000 ; expire 86400 ; ttl ) lforsberg IN A 10.129.51.150 IMG1_SIP IN A 10.129.51.141 PC149_SIP IN A 10.129.51.149 G711 IN A 192.168.19.99 G723 IN A 192.168.19.99 G729 IN A 192.168.19.99 @ IN NS lforsberg


 Create /var/named/10.129.51.zone.

[root@lforsberg named]# more 10.129.51.zone $TTL 86400 51.129.10.IN-ADDR.ARPA. IN SOA lforsberg.gcems_lf.com root.lforsberg.gcems_lf.com ( 10 ; serial 28800 ; refresh 14400 ; retry 3600000 ; expire 86400 ; ttl ) 150.51.129.10.IN-ADDR.ARPA. IN PTR lforsberg.gcems_lf.com. 51.129.10.IN-ADDR.ARPA. IN NS lforsberg.gcems_lf.com.

[root@lforsberg named]#


     
5. Start the DNS service using the following commands:

service named restart

chkconfig named on


3. Use nslookup or dig to test a DNS entry to verify it will resolve the name.  Errors are logged in the /var/log/messages file.


GCEMS ClientView configuration
1. Create the DNS Servers:
          • In the External Network Elements add the DNS Servers object.
          • For the Domain Name enter the domain name of the DNS server. 

2. Create a new DNS server:
          • Enter the name and IP address of the DNS server

3. For each IMG Gateway add the DNS Client. If multiple servers were configured select the primary, secondary and tertiary server.

4. Add a SIP gateway.
          • Gateway Address Type = Host name
          • Gateway IP address. This is required for inbound calls as IMG Gateways do not support reverse DNS lookups. 

Note: if the DNS server is using a pool of addresses for the host name and the IP address returned to a DNS request is not the same as configured below, the call will be rejected.

          • Gateway host name. If the Domain name entered in the DNS servers object is valid, then you only need to enter the host name here: otherwise, you will need to enter the full host.domain name.

5. Debug information can be obtained as follows:
 

> n

zNet> D

 

Server Set Table

DNS Server Set ID 0 Mem Addr:0x171566e0 Domain Suffix:gcems_lf.com

DNS Server Table

Server ID 3 IP:0xa813396 Port:53 NetIF:0xa81338d Server Set:0 Svr Priority:1



6. The following is a sample of data that is added to call trace

09:55:20.154 CALL(SIP) (01:00008:01) SENT DNS QUERY resolve: pc149_SIP to DNS

09:55:20.154 CALL(SIP) (01:00008:01) RCVD DNS QUERY RESOLVED : [10.129.51.149] from DNS

09:55:20.154 CALL(SIP) (01:00008:01) SENT INVITE to pc149_SIP:5060 UDP Cseq:1

09:55:20.154 CALL(SIP) (01:00008:01) with R-URI: pc149_SIP:5060 UDP

09:55:20.154 CALL(SIP) (01:00008:01) and Call-id: 71b7-407-492008145520-E1_System-1-10.129.51.141

09:55:20.344 CALL(SIP) (01:00008:01) RCVD 100 Trying from 10.129.51.149:5060 UDP CSeq:1



Glossary of Acronyms / Terms

DNS - Domain Name Server
FQDN - Fully Qualified Domain Name

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