There is a widly used function called L2PT tunnel to transport transparently some of kind of protocol packets in L2 network. This tunnel is just as if a fiber for the protocol packets.
But there is a small function, the CLI is: l2protocol-tunnel [shutdown-threshold | drop-threshold ] [protocol]
It means if the speed of a kind of protocol in the tunnel reach a threshold, it will shutdown the corresponding interface.
My question is: the tunnel is more like a fiber. Why it should care about the speed of the packets inside, as long as i have enough bandwidth. The shutdown or drop function seems look like a protection of the tunnel or a protection of STP devices using this tunnel.
If this is a protection of two STP devices running on the two sides of the tunnel, this function does not make sense. As the protection should be done by the STP device it self, not rely on the "fiber" between them. They should limit the speed of STP packet it send out.
If this is a protection of the tunnel, why? This is just a transparent tunnel, forward everything received and send out. Some cases might need modify MAC address. But if speed too high, will it be harmful to the device??
I understand the function, but just not clear of the use case.. So could anyone help me? Thanks
