In this section:
The DNS (Domain Name System) group object contains a list of DNS servers used to resolve SIP NAPTR, SRV and A-record look-ups.
The following diagram shows a typical DNS server group configuration.
The SBC supports associating a DNS group with a zone belonging to a different Address Context than that of the DNS group. The DNS query is resolved using the DNS group configured. Refer to Configuring DNS Groups for a configuration example.
You may create up to eight DNS servers. The DNS Client sends the query to the server with highest priority (lower value) first, and in case of a timeout, the query is resent to the server with the next highest priority. For servers with the same priority, the selection is distributed based on the weight value. Priority and weight values are configurable. You can also configure recursion preference (recursion involves assistance from other DNS servers to help resolve the query).
When a DNS group is configured at the Address Context level for an interface, it must also be configured at the Zone level in that Address Context.
To assign a DNS group to a zone, refer to Zone - DNS Group - CLI page.
The SBC Core supports up to eight DNS servers per DNS group. The SBC 5000/7000 series platforms support up to 2,048 DNS Groups system-wide. SBC SWe supports up to 128 DNS Groups. See SBC Provisioning Limits for additional provisioning limitations.
The SBC 52x0 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 51x0 and SBC 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 restriction.)
For complete details, refer to Configuring IP Interface Groups and Interfaces.
You must configure Cluster Admin before configuring D-SBC Signaling Port, Load Balancing Service and DNS Group parameters for intra-cluster VNFC communication.
Refer to Cluster Admin - CLI for configuration details.
Command Syntax
The DSN Group CLI syntax is shown below:
% set addressContext <addressContext name> dnsGroup <dnsGroup name> ednsSupport <disabled | enabled> interface <interface name> localRecord <record name> data <#> hostName <name> order <centralized-roundrobin | priority | roundrobin> state <disabled | enabled> server <DSN server name> ipAddress <ip address> priority <0-100> recordOrder <centralized-roundrobin | priority | roundrobin> recursionDesired <false | true> state <disabled | enabled> tcpFallback <disabled | enabled> transportProtocol <tcp | udp> weight <0-100> transport <tcp | udp> type <ip | mgmt | none> useConfiguredDnsServer <disabled | enabled>
CLI syntax to configure the type of IP interfaces to be used for this DNS Group:
% set addressContext <addressContext name> dnsGroup <dnsGroup name> type <ip | mgmt | none>
CLI syntax to configure the local DNS resource record:
% set addressContext <addressContext name> dnsGroup <dnsGroup name> localRecord <record_name> data <index#> ipAddress <ip address> priority <0-100> state <disabled | enabled> type <a | aaaa> hostName <host_Name> order <centralized-roundrobin | priority | roundrobin> state <enabled | disabled>
CLI syntax to configure the DNS server for this address context:
% set addressContext <addressContext name> dnsGroup <dnsGroup name> server <DNS server name> ipAddress <DNS_ipAddress> priority <0-100> recordOrder <centralized-roundrobin | priority | roundrobin> recursionDesired <false | true> state <disabled | enabled> tcpFallback <disabled | enabled> transportProtocol <tcp | udp> weight <0-100>
CLI syntax to configure and display the type of IP interfaces to be used for this DNS Group:
% set addressContext <addressContext_name> dnsGroup <dnsGroup_name> type ip -OR- % set addressContext <addressContext_name> dnsGroup <dnsGroup_name> type mgmt interface mgmtGroup % show addressContext <addressContext_name> dnsGroup <dnsGroup_name> type
The SBC supports, by default, 1,300 Maximum Transmission Unit (MTU) bytes, and the MTU size used by the SBC is configurable. If the initial INVITE message size exceeds the default MTU value, the SBC sends the data over the TCP transport protocol. The TCP transport protocol is used if it is allowed by the transport profile irrespective of its preference order.
Go to Configuring DNS Groups page for example DNS configurations.