Related Documentation
Layer 2 Port Mirroring Overview
On routing platforms that contain an Internet Processor II ASIC, you can send a copy of any incoming packet from the routing platform to an external host address or a packet analyzer for analysis. This is known as port mirroring. In Junos OS Release 9.3 and later, Juniper Networks MX Series 3D Universal Edge Routers in a Layer 2 environment support port mirroring for Layer 2 bridging traffic and virtual private LAN service (VPLS) traffic. In Junos OS Release 9.4 and later, MX Series routers in a Layer 2 environment also support port mirroring for Layer 2 VPN traffic over a circuit cross-connect (CCC) that transparently connects logical interfaces of the same type.
Layer 2 port mirroring enables you to specify the manner in which incoming and outgoing packets at specified ports are monitored and the manner in which copies of selected packets are forwarded to another destination, where the packets can be analyzed. MX Series routers support Layer 2 port mirroring by performing flow monitoring functions using a class-of-service (CoS) architecture that is in concept similar to, but in particulars different from, other routing platforms.
Like the M120 Multiservice Edge Router and M320 Multiservice
Edge Routers, MX Series routers support port mirroring of IPv4, IPv6,
and VPLS packets simultaneously. However, the Junos OS Layer 2 Configuration Guide 
describes
port mirroring only for Layer 2 bridging traffic (family bridge), Layer 2 VPLS traffic (family vpls) through an MX
Series router, and Layer 2 VPN traffic that passes through a
CCC (family ccc).
For general information about packet flow within MX Series routers
and other routers, see the Junos OS Class of Service Configuration Guide .
In a Layer 3 environment, MX Series routers support port
mirroring of IPv4 (family inet) and IPv6 (family inet6) traffic. For information about Layer 3 port mirroring, see
the Junos OS Policy Framework Configuration Guide .
