This section tells you how to access and set the values you need depending on the configuration mechanism you choose. It also provides sample configurations for your reference.

Configuring DNS ALG service requires that you carry out two main procedures:

• Setting the name, realm, and DNS service IP interfaces
• Setting the appropriate parameters for DNS servers to use in other realms

1. Configure the client realm that you are going to use in the main DNS ALG profile and note its name to use in this chapter’s configuration process.
2. Configure the server realm that contains the DNS servers and note its name to use in this chapter’s configuration process.
3. Determine the domain suffixes for the network where the DNS servers are located so that you can enter them in the domain suffix parameter.
4. Devise the NAT scheme that you want to use when the DNS reply transits the Oracle Communications Session Border Controller.

1. description—Set a name for the DNS ALG profile using any combination of characters entered without spaces. You can also enter any combination with spaces if you enclose the whole value in quotation marks. For example: DNS ALG service.
2. client-realm—Enter the name of the realm from which DNS queries are received. If you do not set this parameter, the DNS ALG service will not work.
3. client-address-list—Configure a list of one or more addresses for the DNS server interface. These are the addresses on the Oracle Communications Session Border Controller to which DNS clients send queries.

   To enter one address in this list, type client-address-list at the system prompt, a Space, the IPv4 address, and then press Enter

   ORACLE(dns-config)# client-address-list 192.168.0.2

   To enter more than one address in this list, type client-address-list at the system prompt, and a Space. Then type an open parenthesis ( ( ), each IPv4 address you want to use separated by a Space, and closed parenthesis ( ) ), and then press Enter.

   ORACLE(dns-config)# client-address-list (192.168.0.2 196.168.1.1 192.168.1.2)

1. In Superuser mode, type configure terminal and press Enter.

   ORACLE# configure terminal

2. Type media-manager and press Enter.

   ORACLE(configure)# media-manager

3. Type dns-config and press Enter. The system prompt changes to let you know that you can begin configuring individual parameters.

   ORACLE(media-manager)# dns-config

4. Type server-dns-attributes and then press Enter.

   ORACLE(dns-config)# server-dns-attributes

   From this point, you can configure DNS server parameters. To see all parameters for the DNS server, enter a ? at the system prompt.

5. server-realm—Enter the name of the realm in which the DNS server is located. This value is the name of a configured realm.
6. domain-suffix—Enter a list of one or more domain suffixes to indicate the domains you want to serve. These values are matched when a request is sent to a specific DNS server. If you leave this list empty (default), then your configuration will not work.

   Note:

   If you want to use a wildcard value, you can start your entry to an asterisk ( * ) (e.g. *.com). You can also start this value with a dot (e.g., .com).

   To enter one address in this list, type client-address-list at the system prompt, a Space, the domain suffix, and then press Enter

   ORACLE(server-dns-attributes)# domain-suffix acmepacket.com

   To enter more than one address in this list, type domain-suffix at the system prompt, and a Space. Then type an open parenthesis ( ( ), each IPv4 address you want to use separated by a Space, and closed parenthesis ( ) ), and then press Enter.

   ORACLE(server-dns-attributes)# domain-suffix (acmepacket.com acmepacket1.com acmepacket2.com)

7. server-address-list—Enter a list of one or more DNS IPv4 addresses for DNS servers. These DNS servers can be used for the domains you specified in the domain suffix parameter. Each domain can have several DNS servers associated with it, and so you can populate this list with multiple IPv4 addresses. If you leave this list empty (default), your configuration will not work.
8. source-address—Enter the IPv4 address for the DNS client interface on the Oracle Communications Session Border Controller. If you leave this parameter empty (default), your configuration will not work.
9. source-port—Enter the number of the port for the DNS client interface on the Oracle Communications Session Border Controller. The default value is 53. The valid range is:

   • Minimum—1025

   • Maximum—65535

10. transaction-timeout—Enter the time in seconds that the ALG should keep information to map a DNS server response back to the appropriate client request. After the transaction times out, further response to the original request will be discarded. The default value is 10. The valid range is:

    • Minimum—0

    • Maximum—999999999

11. address-translation—Enter a list of address translations that define the NAT function for the DNS servers.

    You can access the NAT parameters for the DNS servers by typing address-translation and pressing enter within the DNS server attributes configuration.

    ORACLE(dns-config)# server-dns-attributes
    ORACLE(server-dns-attributes)# address-translation

    To configure the NAT, enter two values:

    • server-prefix: address/prefix that will be returned by the DNS server

    • client-prefix: address/prefix that to which a response is returned

      Each of these is a two-part value:

    • IPv4 address

    • Number of bits indicating how much of the IPv4 address to match

      If you do not specify the number of bits, then all 32 bits of the IPv4 address will be used for matching. If you set the number of bits to 0, then the address will simply be copied.

      For example, if you set the server prefix to 10.3.17.2/16 and the client prefix to 192.168.0.0/16, then the Oracle Communications Session Border Controller will return an address of 192.168.17.2 to the DNS client.

      ORACLE(server-dns-attributes)# address-translation
      ORACLE(address-translation)# server-prefix 10.3.17.2/16
      ORACLE(address-translation)# client-prefix 192.168.0.0/16

1. In Superuser mode, type configure terminal and press Enter.

   ORACLE# configure terminal
   ORACLE(configure)#

2. Type media-manager and press Enter

   ORACLE(configure)# media-manager
   ORACLE(media-manager)#

3. Type media-manager and press Enter.

   ORACLE(media-manager)# media-manager
   ORACLE(media-manager-config)#

4. dnsalg-server-failover—Change this parameter from disabled (default) to enabled to allow DNS queries to be sent to the next configured server—even when contacting the Oracle Communications Session Border Controller’s DNS ALG on a single IP address. So when the first server in the list times out, the request is sent to the next server in the list. The Oracle Communications Session Border Controller uses the transaction timeout value set in the dns-server-attributes configuration (part of the dns-config).
5. Save your work.

After the first failed attempt to reach a DNS server, The Oracle Communications Session Border Controller places it in a Time Out state. The server stays in Time Out state for 30 seconds. The Oracle Communications Session Border Controller does not send DNS queries to a server in Time Out state. Instead, it directs queries to the next DNS server in the server-address-list. After 30 seconds, the DNS server goes back to an In Service state and the Oracle Communications Session Border Controller sends queries to it.

If a DNS server fails to respond to 5 consecutive queries, it goes into Out of Service (OOS) state. The Oracle Communications Session Border Controller directs all subsequent queries to the first In Service server. The Oracle Communications Session Border Controller returns OOS DNS servers to In Service state after 600 seconds and repeats the cycle above. If, for any given call, all configured DNS servers are OOS, the Oracle Communications Session Border Controller fails the call.