This section outlines the necessary settings for using DNS through the GETDNS resolver instance. The configuration differs depending on whether the GETDNS is accessible locally or remotely under BS2000 or another platform.
Starting the DNS-CLIENT
By default, the DNS-CLIENT GETDNS starts implicitly with the standard configuration file during DCSTART (/DCSTART or /DCOPT with DNS-CLIENT=*YES). Alternatively, GETDNS can be started after BCAM using the START-DNS-CLIENT command.
Note:
If DNS is not being used or GETDNS is running remotely, starting GETDNS is not mandatory (/DCSTART or /DCOPT with DNS-CLIENT=*NO). However, it is recommended to have GETDNS running on the system to avoid unwanted timeout delays during name resolution (e.g., for the FTP server).
Configuring GETDNS
Configuration file: SYSDAT.SOCKETS.nnn.RESOLV.CONF
At least one accessible and functional DNS server must be entered and the domains to be used should be included. A detailed description of GETDNS and its settings can be found in chapter "DNS Resolver connection".
Note:
When GETDNS is reachable remotely, an entry in the GETDNS configuration file is not strictly necessary but advisable. This way, when using DIG and NSLOOKUP, no server specification is required.
Ensure accessibility of the DNS servers
To ensure GETDNS can contact the DNS servers listed in its configuration file (SYSDAT.SOCKETS.nnn.RESOLV.CONF), there must be a working connection to all DNS servers. This can be managed via Automatic End-System Inclusion (AEC) with appropriate entries in a system file (see the chapter "Automatic end system creation") or through manual definitions (see the chapter "Dynamic generation with BCAM commands").
Enable GETDNS server (GETDNS remote)
When using GETDNS remotely, the IP/IPv6 address and port of GETDNS (if different from the standard port) must be enabled for BCAM using the MODIFY-DNS-ACCESS command (operand DNS-RESOLVER). If the GETDNS server also runs on BS2000, these entries must be made on that host as well.
Allow DNS use
The use of the Domain Name System (via GETDNS) for the automatic endsystem creation must be explicitly activated in BCAM:
/MODIFY-BCAM-OPTIONS DNS-OPTIONS=*PARAMETERS(DNS-USAGE=*ON)
You can use /SHOW-DNS-ACCESS to display the current settings.
Note:
This setting applies only to DNS usage by BCAM during AEC, not to DNS usage by Sockets applications on the system.
Restrictions on DNS access
With the /MODIFY-DNS-ACCESS command, you can restrict DNS access, specifically AEC via DNS, for certain IP/IPv6 addresses or BCAM names. Detailed information about this command and its settings can be found in the section "MODIFY-DNS-ACCESS".