Finding the OID:
1- search for the SNMPcounter "ifOutUcastPkts"
2- use the cli command: "show mib get "+ "| display xml "
https://apps.juniper.net/mib-explorer/
...
https://www.manageengine.com/products/mibbrowser-free-tool/
Q-BRIDGE-MIB refers only to internal VLAN indexes,
you need to use both MIBs to get Port/VLAN mappings including the 802.1Q VLAN tag ID (jnxExVlanTag).
1- define the Interface SNMP Index ( show interface ...)
...
{master:0}
readonly@EX4300-Client-1-Active> show snmp mib walk 1.3.6.1.2.1.17.1.4
show snmp mib get ifIndex.536
show snmp mib get ifDescr.536
show snmp mib get ifInOctets.536
show snmp mib get ifInUcastPkts.536
show snmp mib get ifOutOctets.536
show snmp mib get ifOutUcastPkts.536
XML Display:
family ethernet-switching:
...