You can configure one (1) mirror to analyze traffic. Configure the source/destination port (input/output port).
Note: The output (mirroring) port can belong to any VLAN and will not participate in Layer2 or Layer3 forwarding.

Configuring Mirroring to Analyze Traffic

admin@XorPlus# set interface ethernet-switching-options analyzer 111 input egress ge-1/1/1 
admin@XorPlus# set interface ethernet-switching-options analyzer 111 input ingress ge-1/1/1 
admin@XorPlus# set interface ethernet-switching-options analyzer 111 input egress ge-1/1/2
admin@XorPlus# set interface ethernet-switching-options analyzer 111 input ingress ge-1/1/2
admin@XorPlus# set interface ethernet-switching-options analyzer 111 output ge-1/1/3
admin@XorPlus# commit 
Waiting for merging configuration.
Commit OK.
Save done.
admin@XorPlus# run show analyzer 111 
Analyzer name: 111 
Output interface: <ge-1/1/3>
Ingress monitored interfaces: <ge-1/1/1><ge-1/1/2>
Egress monitored interfaces: <ge-1/1/1><ge-1/1/2>
admin@XorPlus#