What is the purpose of the qos pre-classify command?
A.
to enable the IOS to copy the ToS field from the original IP header to the outer tunnel IP header
B.
to enable the IOS to copy the ToS field from the outer tunnel IP header back into the original IP header
C.
to enable the IOS to classify the packet based on the original IP header instead of the tunnel IP header
D.
to enable the IOS to classify the packet based on the outer tunnel IP header instead of the original IP header
E.
to enable class-based marking on tunnel interface
F.
to enable class-based marking on IPSec crypto maps
Explanation:
For Layer 2 Forwarding(L2F) and Layer 2 Tunneling Protocol(L2TP) protocols, the qos pre-classify command is applied on the virtual template interface. L2TP clients belonging to identical virtual private dial-up network (VPDN) groups inherit the preclassification setting. The qos pre-classify command can be configured on a per-VPDN tunnel basis.
For IPSec tunnels, the qos pre-classify command is applied on the crypto map, allowing configuration on a per-tunnel basis. QoS features on the physical interface carrying the crypto map are able to classify packets before encryption.
Reference:
http://www.cisco.com/en/US/products/sw/iosswrel/ps1835/products_configuration_guide_chapter0 9186a00800c75d3.html