Which mechanism keeps a switch from forwarding Layer 2 traffic from one broadcast domain to another?

Which mechanism keeps a switch from forwarding Layer 2 traffic from one broadcast domain to another?

A.
filtering

B.
BPDU guard

C.
aging

D.
learning

Explanation:
Defining a Layer2 Port-Mirroring Firewall Filter

For virtual private LAN service (VPLS) traffic (familybridge or familyvpls) and for Layer 2 VPNs with familyccc on MX Series routers only, you can define a firewall filter that specifies Layer2 port mirroring as the action to be performed if a packet matches the conditions configured in the firewall filter term.

You can use a Layer2 port-mirroring firewall filter in the following ways:

* To mirror packets received or sent on a logical interface.
* To mirror packets forwarded or flooded to a bridge domain.
* To mirror packets forwarded or flooded to a VPLS routing instance.
* To mirror tunnel interface input packets only to multiple destinations.

For a summary of the three types of Layer 2 port-mirroring you can configure on an MX Series router, see Application of Layer 2 Port Mirroring Types.