Grid members can use database replication to maintain up-to-date zone data sets, so the secondary servers in the Grid can keep their zone data synchronized even if the primary server fails. Any external secondary servers can fall out of sync, however, if they rely only on the primary server to send notify messages when there is new zone data. Therefore all authoritative name servers in a Grid (all primary and secondary servers) send notify messages to external secondary servers by default. This ensures that an external secondary name server receives notify messages when its master primary server is a secondary name server in a Grid. However, it also increases the number of notify messages.
Infoblox recommends that you do not configure a large number of external secondary servers in stealth mode. To ensure that these secondary servers receive notifications about zone updates, you can allow zone transfers for these IP addresses and then enable the appliance to add them to the also-notify statement. For information about how to configure this feature, see Configuring Zone Transfers.
To specify whether secondary name servers in the Grid are to send notify messages to external secondary name servers:
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For the external secondary servers to accept notify messages from the secondary name servers in the Grid and then request zone transfers from them, you must configure the external secondary servers to use the Grid secondary servers as the source of the zone transfers. This ensures that the external secondary servers continue to receive notify messages, even if the primary server is unavailable.
NIOS 8.1NIOS Administrator Guide (Rev. A)789
Configuring DNS Services