support matrix in https://www.juniper.net/documentation/en_US/junos/topics/topic-map/management-interface-in-non-default-instance.html#tabel-support-management-vrf

SNMP

cloudsw hosts, QFX running Junos 18.4, with management-instance configured and being pulled through em0, were full of those logs:

Dec 3 07:00:39 cloudsw1-c8-eqiad snmpd[2335]: SNMPD_AUTH_RESTRICTED_ADDRESS: nsa_initial_callback: request from address 208.80.154.88 not allowed

Even though everything seems to be pulled correctly.

The fix (or workaround) is to add routing-instance mgmt_junos to the relevant matching community.

# show snmp 
location eqiad;
community [redacted] {
    authorization read-only;
    routing-instance mgmt_junos;
}
routing-instance-access;

NTP

Dec 3 10:00:03 cloudsw1-c8-eqiad xntpd[19552]: NTP Server 208.80.153.77 is Unreachable

[edit system ntp server 208.80.153.77]
+    routing-instance mgmt_junos;

DNS

Starting in Junos OS Release 19.2R1, you can route traffic between a management routing instance and DNS name server. Configure a routing instance at the [edit system name-server server-ip-address] hierarchy level and the name server becomes reachable through this routing instance.

It is possible to configure it though, but it doesn't work:

[edit system name-server 10.3.0.1]
+   routing-instance mgmt_junos;

Syslog

[edit system syslog]
+   routing-instance mgmt_junos;

But as we use FQDNs for syslog targets, it won't work. Need to replace it with IPs for now on.
Relevant: T268806#6663995