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TR7Enterprise Application Delivery & Security Platform
What is DNS NOTIFY?
Short answer
DNS NOTIFY is the master server sending slave servers a "there is a new version of the zone" notification when the zone changes (RFC 1996). The slave that receives the notification checks the SOA serial and, if necessary, starts a zone transfer; in this way the slaves are updated without waiting for the SOA refresh time. TR7 GTM uses NOTIFY in both directions. In the master role, it sends NOTIFY to the addresses in the Slave Server IPs list whenever there is a change in the domain. In the slave role, with the NOTIFY coming from the master server of the Express Profiles profile assigned to the domain, it starts a zone transfer from that master; the incoming notifications are monitored in the DNS service dashboard's DNS Traffic Events panel, in its Notifications series.
Where It Is Used in TR7
| Where | Field / label | What for |
|---|---|---|
| GTM → GTM Services → service name → Domains → Add / Edit | Slave Server IPs | The slave servers to which NOTIFY will be sent when the domain changes and to which the zone transfer permission will be given |
| GTM → Express Profiles (DNS Integration) | Master Addresses | The master servers whose NOTIFY will be accepted; only the notifications coming from these addresses start the synchronization |
| GTM → GTM Services → service name → Dashboard → Traffic | DNS Traffic Events → Notifications series | The number of NOTIFYs arriving per second |
| GTM → GTM Services → service name → Records | Express Logs | The <domain> <master IP> notified AXFR line and the transfer results that follow it |
- On the Express side, the notifications arriving within 5 seconds for the same domain are combined and processed once more within 10 seconds at the latest; since there is no timer-based refresh, if the master does not send NOTIFY, the refresh is done only with Sync via Express.
Common Misconceptions
- "NOTIFY carries the records." NOTIFY is only a notification; the records are transferred with the zone transfer made after it.
- "Without NOTIFY, the slaves are never updated." Standard slave servers also check at the SOA refresh time; NOTIFY only shortens the wait. The Express side of TR7, however, does not use a timer.
- "NOTIFY coming from any address is accepted." On the TR7 Express side, only the notifications coming from the master addresses of the Express profiles bound to the domain start the synchronization.
How it is done in the documentation
