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Use this window to create and configure a DNS (Domain Name System) group object. This object represents a DNS client on the SBC capable of communicating with external DNS servers to resolve domain names.


Note

Each signaling port within an Address Context must use a unique IP address and port number combination.


Note

The SBC 5210 and SBC 7000 systems support creating IP Interface Groups containing sets of IP interfaces that are not "processor friendly" (i.e. carried on physical Ethernet ports served by separate processors). However, restrictions exist regarding the usage of such Interface Groups.

(This ability does not apply to the SBC 5110 and 5400 systems which have only two physical media ports. IP interfaces from the two physical ports may be configured within the same IP Interface Groups without restrictions.)

For complete details, refer to Configuring IP Interface Groups and Interfaces.


Note

The SBC Core supports up to eight DNS servers per DNS group. The SBC 5x10/5400/7000 platforms support up to 2,048 DNS Groups system-wide. The SBC SWe supports up to 128 DNS Groups. Refer to SBC Provisioning Limits for additional provisioning limitations. 

To View DNS Groups

On the SBC main screen, go to Configuration > System Provisioning > Category: Base Provisioning > DNS > Servers > DNS > DNS Group or 
All > Address Context > DNS Group. The  DNS Group window is displayed. Select an Address Context to display only the DNS Groups configured within the selected Address Context.

Figure 1: DNS Group


To Create a DNS Group

To create a new DNS Group:

  1. In the DNS Group window, select the Address Context within which you want to create the DNS Group.   

  2. Click New DNS Group. The Create New DNS Group window is displayed.
    Figure 2: Create New DNS Group Window

  3. Use the following table to configure the options and then click Save.
    Table 1: DNS Group Parameters

    Parameter

    Description

    Name

    Specify the name for the DNS Group of upto 23 characters. This field is mandatory.

    Type

    Specify the interface type to use for DNS queries. The options are:

    • IP

    • Mgmt

    • None (default)


    Based on the type chosen, the additional options open.

    Transport

    Select the transport protocol to communicate with the DNS servers.

    • UDP (default)

    • TCP 

    Mgmt Interface

    Select the management interface group for the management interfaces.

    Note: This field displays only when the selected Type  is Mgmt.

    IP Interface

    Select the IP interface group for the packet interfaces.

    Note: This field displays when the selected Type is IP.

    Use Configured Dns Server

    When this flag is disabled,  the SBC stores "Authoritative" NS records received in Domain Name System (DNS) query responses and uses them to locate a closer DNS server for subsequent DNS queries. There are cases where an “Authoritative” server might not be directly reachable from the SBC, or IP ACL rules ( configured on the SBC) blocks its query responses. This block causes the DNS queries to fail and subsequent call failures.

    When this flag is enabled, the SBC supports using the configured DNS for external the DNS queries within that DNS group. It sends the DNS queries to the DNS server in the DNS group and ignores Authoritative servers.The options are:

    • Disabled (default)

    • Enabled

    Edns Support

    Enable this flag to support Extension mechanisms for Domain Name Systems (EDNS) for statically configured and dynamically learned DNS servers. The options are:

    • Disabled (default) 

    • Enabled

    DNS Fallback

    Disable this flag to send an EDNS request towards the DNS server irrespective of any DNS failure response received in the past.

    If this flag is enabled and EDNS failure error response is received for a query, then the SBC stops sending further EDNS requests towards the DNS server. Instead, regular DNS query is sent to the DNS server.

    Refer to sonusSbxDnsServerEdnsFailureNotification - CRITICAL, for additional details.

    • Disabled 
    • Enabled (default)
    Rcode Error Monitor Timer

    Configure the RCODE error monitor timer interval to allow the SBC to monitor RCODE errors. When the timer value is 0, this feature is disabled.

    Range: 0 - 60 minutes

    Default: 0 minutes

    Negative Dns Cache Support

    Enable this flag for the SBC to store records in the negative cache in case a failure occurs in order to receive a 'DNS Successful' lookup response. No external DNS queries are sent for the same record until it is in a negative cache state.

    • Disabled
    • Enabled (default)

    NOTE: If you require that the SBC sends the DNS lookup queries to the external DNs server for each call even if DNS queries failed previously, you must disable this flag.

    NOTE: Use this flag, in conjunction with Dnslookup Timeout Timer and Negative Dns Cache Timer parameters, to manage how DNS lookups are sent to the negative cache.

    Negative Dns Cache Timer

    Use this timer to set a length, in seconds, to keep DNS lookup failed records in the negative cache.

    Range: 10-300 seconds

    Default: 60 seconds

    NOTE: This parameter is only available when the Negative Dns Cache Support flag is enabled.

    Dnslookup Timeout Timer

    Use this timer for DNS lookup messages to set an expiration time, in seconds, after which a DNS query fails.

    Range: 10-300 seconds

    Default: 10 seconds

    NOTE: If your network includes several DNS servers configured with higher retransmission count values, increase this timer value based on the DNS global retransmission count and retransmission timer settings.

To Edit a DNS Group

To edit a DNS Group object:

  1. Click the option button next to the DNS Group you want to edit. The Edit DNS Group window opens.
  2. Modify the options as needed and click Save.

To Delete a DNS Group

To delete a DNS Group:

  1. Click the option button next to the DNS Group that you want to delete.
  2. Click the Delete icon at the end of the highlighted row. 
  3. Confirm the deletion when prompted.


Note

Before deleting a DNS group, first delete the DNS local records and DNS servers in that group.

DNS Group Commands

Use DNS Group commands to perform manual actions against a configured DNS Group.

To use DNS Group commands for any specific DNS Group, select the option next to the specific DNS Group. The DNS Group Commands window is displayed at the bottom of the window.

Figure 3: DNS Group Commands


Clear Cache

Use the Clear Cache command to clear the cache of a specified record.

  1. Choose Clear Cache in the Commands list and click Select. A clearCache dialog box opens.
    Figure 4: Clear Cache


  2. In Domain Name text box, enter the name of the domain record you want to clear from the cache.
  3. In Record Type drop-down, select the type of DNS record to clear. The options are:
    • A
    • Aaaa
    • Ns
    • Srv
    • Naptr
    • Default (default)
  4. Click clearCache.

DNS Server Reset

Use the DNS Server Reset command to reset all the DNS server statistics.

  1. Choose DNS Server Reset  in the Commands list and click Select. A dnsServerReset dialog box opens.
  2. Click dnsServeReset.
  3. Confirm the action at the prompt.

Query

Use the Query command to send a DNS query to a specified server.

  1. Choose Query in the Commands list and click Select. A query dialog box is displayed.
    Figure 5: Query Command


  2. Use the following table to enter parameters for the query and click query.
    Table 2: Query Parameters

    ParameterDescription
    DNS ServerEnter the name of the DNS Server to perform lookup.
    FQDNEnter the domain to perform look up.
    Record Type

    Specifies the type of DNS records.

    • A (default)
    • Aaaa
    • Ns
    • Srv
    • Naptr

Update Ttl

Use the Update Ttl command to to update the TTL (Time To LIve) value in the cache for a specified record.

  1. Choose Update Ttl in the Commands list and click Select. An update Ttl dialog box is displayed.
    Figure 6: Update Ttl Command


  2. Use the following table to select the record to update and click updateTtl.
    Figure 7: Update Ttl Parameters

    ParameterDescription
    FQDNEnter the FQDN whose record to update in the cache.
    Record Type

    Specifies the type of DNS records.

    • A (default)
    • Aaaa
    • Ns
    • Srv
    • Naptr
    TtlEnter a new TTL value.