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kardianos
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Joined: Tue Sep 07, 2021 4:47 pm

7.1rc2 - Negative DNS cache for all record types, even if CNAM exists

Tue Sep 07, 2021 5:00 pm

Hello,

I am running 7.1.rc2.
I suspect there is a bug in negative DNS Caching when:

There is a remote (externally accessible) CNAME that points to a local A Record.

For example:

External (globally accessible) DNS:
my.domain.com CNAME __ip.domain.com
__ip.domain.com A 1.2.3.4

Mikrotik:
__ip.domain.com A 192.168.100.50

The goal is to resolve the same domain name to either an internal IP address or an external IP address. Rather then listing out A records locally and externally, use a CNAME to point to either internal or external IP.

When I try to resolve "my.domain.com" from within the LAN, the Mikrotik router places a "negative" DNS entry, despite it being able to resolve it. Or rather, it fails to resolve an A record, but places a negative record for all DNS types.

One way to fix this is to manually place A records internally, rather then using a CNAME to an A record.

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