This article provides an example of an expected behavior where the same MAC address is learned in multiple ports of the switch.
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root@QFX-1# run show ethernet-switching table
TI-BMW-VnA fc:96:43:xx:xx:xx D - et-0/0/48.0 0 0
TI-BMW-VnB fc:96:43:xx:xx:xx D - et-0/0/49.0 0 0
TI-BMW-VnC fc:96:43:xx:xx:xx D - et-0/0/50.0 0 0
This behavior is expected in the below scenario:
irb.20 EX3400 --- et-0/0/48 vlan VnA--- QFX5100
irb.22 EX3400 --- et-0/0/49 vlan VnB --- QFX5100
irb.24 EX3400 --- et-0/0/50 vlan VnC --- QFX5100
The EX3400 is going to use the MAC of the irb interface, and since the ports et-0/0/48, et-0/0/49 and et-0/0/50 are passing different vlans, the bridge domain is different and therefore the MAC is not considered duplicate.
root@EX3400> show interfaces irb | match current
Current address: fc:96:43:xx:xx:xx, Hardware address: fc:96:43:xx:xx:xx
root@QFX-1# run show arp no-resolve
MAC Address Address Interface Flags
fc:96:43:xx:xx:xx 1.31.20.2 irb.20 [et-0/0/48.0] none
fc:96:43:xx:xx:xx 1.31.22.2 irb.22 [et-0/0/49.0] none
fc:96:43:xx:xx:xx 1.31.24.2 irb.24 [et-0/0/50.0] none