Niall O'Reilly niall.oreilly at
Wed Aug 1 11:09:33 UTC 2018

On 1 Aug 2018, at 10:01, Mohammed Ejaz wrote:

> Is there any way to troubleshoot from the master server why there is 
> no synchnization to one more Slave.

Only partly. You may need access to the slave at some stage.

Master log should record NOTIFY messages sent to all slaves.
If not all desired slaves are being sent NOTIFY, master needs to be
configured with relevant directive (BIND named: also-notify).

If master is sending NOTIFY, next thing to check is whether slave
is requesting AXFR/IXFR. Master log should show each transfer.
If not, then you’ll need to ask sysadmin at slave to check whether
NOTIFY is arriving and being accepted, and whether slave is actually
requesting transfer. If not, slave configuration may need
correction (BIND named: allow-notify).

If there is still a problem, you’ll likely need to use tcpdump or
the like to investigate at network level, as NOTIFY or transfer
may be blocked by a misconfigured firewall or other network fault.

One other thing: avoid using nslookup. In trying to be “helpful”,
it hides significant information and makes troubleshooting difficult.
You’ll save time (yours, and that of anyone who tries to help you)
by using dig.

Best regards,
Niall O’Reilly

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