Downstream DNS configuration settings for networks

At any time after you create a network, you can change its downstream DNS configuration settings to:

Enable hidden master for one or more downstream DNS servers

Enable notify for one or more downstream DNS servers

Change the DNS refresh rate for all the downstream DNS servers

A downstream DNS server is a DNS server through which client requests are routed to HCP. An upstream DNS server is a DNS server to which HCP routes the outbound communications it initiates (for example, for sending log messages to syslog servers or for communicating with Active Directory). The downstream and upstream DNS servers can be the same servers.

Hidden master

Hidden master is an HCP DNS configuration that’s used to hide the IP addresses of the HCP nodes configured as master name servers from users accessing HCP over a specific network. In a hidden master configuration, the specified downstream DNS servers become the authoritative masters for the zone defined for the network domain. Additionally, in the zone definition that HCP sends, the name server records contain the IP addresses of the downstream DNS servers, and not the IP addresses of the HCP nodes configured as master name servers.

Notify

Notify is a network configuration option that, when enabled for a network, tells HCP to notify only the specified downstream DNS servers whenever any of the network properties changes (including the description). In response to this notification, each specified DNS server sends a request to HCP to get the updated zone definition for the network domain.

Zone definitions with hidden master or notify enabled

When hidden master or notify is enabled for a network, the domain associated with that network must be defined as a secondary zone (also called a slave zone), and not as a stub zone, on the specified downstream DNS servers. If a network domain is defined as a stub zone and:

You enable hidden master for the network, client requests routed to any of the specified DNS servers fail

You enable notify for the network, the specified DNS servers do not receive the notify messages

If a stub zone is already defined for a domain associated with a network, and you plan to enable hidden master or notify for that network, change the DNS zone definition type for the domain to secondary before you modify the network.

When hidden master or notify is enabled for a network that’s configured to use a secondary IPv6 subnet, each IPv6 address that’s specified in the downstream DNS server list must either be on the secondary IPv6 subnet or be routable from the primary IPv6 gateway that’s defined for the network.

For more information on zone definitions for HCP, see Configuring DNS for HCP.

Refresh rate

The refresh rate for a network is the frequency with which the downstream DNS servers poll HCP to check whether the zone definition for the network domain has changed. If the definition has changed, the servers then ask HCP for the updated definition.

The refresh rate always applies to all the downstream DNS servers that have a zone definition for the network domain and is used regardless of whether that zone definition has a type of secondary or stub.

By default, the refresh rate is three hours. If you enable notify and specify all the applicable DNS servers, consider increasing the refresh rate to a much higher value.

Notify does not work with stub zones. Therefore, if the domain is defined as a stub zone, consider decreasing the refresh rate. If DNS failover occurs, the shorter refresh rate may allow clients targeting a failed system over the network to be more quickly redirected to another system in the replication topology. For information on DNS failover, see Replicating Tenants and Namespaces.

You specify the refresh rate for a network as any combination of weeks (W), days (D), hours (H), minutes (M), and seconds (S), using this syntax:

#W#D#H#M#S

These considerations apply:

In each case, # must be an integer greater than or equal to one.

If an integer is specified without a time unit, the time unit is assumed to be seconds.

Time units can be specified in any order.

Any given time unit can be specified only once.

Time units are not case sensitive.

The total time specified must be in the range one through 2,147,483,647 seconds.

Trademarks and Legal Disclaimer

© 2017 Hitachi Data Systems Corporation. All rights reserved.