The IRB interfaces in two different vMX have the same MAC addresses.
The IRB interfaces MAC address is allocated from chassis MAC address pool for private address. The command below shows the output from two vMX deployed on VMWare ESXi
root@vMX2> show chassis mac-addresses MAC address information: Public base address 2c:6b:f5:3c:15:00 Public count 1984 Private base address 2c:6b:f5:3c:1c:c0 Private count 64 root@vMX2> show interfaces irb Physical interface: irb, Enabled, Physical link is Up Interface index: 132, SNMP ifIndex: 512 Type: Ethernet, Link-level type: Ethernet, MTU: 1518 Device flags : Present Running Interface flags: SNMP-Traps Link type : Full-Duplex Current address: 2c:6b:f5:3c:1c:f0, Hardware address: 2c:6b:f5:3c:1c:f0 Last flapped : Never Input packets : 0 Output packets: 0 root@vMX1> show chassis mac-addresses MAC address information: Public base address 2c:6b:f5:3c:15:00 Public count 1984 Private base address 2c:6b:f5:3c:1c:c0 Private count 64 root@vMX1> show interfaces irb Physical interface: irb, Enabled, Physical link is Up Interface index: 132, SNMP ifIndex: 512 Type: Ethernet, Link-level type: Ethernet, MTU: 1518 Device flags : Present Running Interface flags: SNMP-Traps Link type : Full-Duplex Current address: 2c:6b:f5:3c:1c:f0, Hardware address: 2c:6b:f5:3c:1c:f0 Last flapped : Never Input packets : 0 Output packets: 0
This is expected behavior. The MAC address for the IRB can be changed manually using the command below:
set interfaces irb unit <unit-number> mac <mac-address>