CCNP Practice Question: Given the following configuration: policy-map…

Answer analysis

Option-by-option breakdown

For each option: why learners choose it and why it is or isn't the right answer here.

• ✓

  It sets the DSCP value to 0, which is the default best-effort marking.

  Why this is correct

  The `set dscp 0` command explicitly overwrites the Differentiated Services Code Point bits with binary 000000. DSCP 0, also known as CS0 or default PHB, is the standard best-effort marking applied to normal IP traffic. Because this is an explicit action in a policy-map, it always results in DSCP 0 regardless of any original marking.

• ✗

  It sets the DSCP value to the original value of the packet, effectively not changing it.

  Why it's wrong here

  This option confuses an explicit marking instruction with a 'copy' or 'preserve' behavior. The `set dscp 0` action does not read the packet's current DSCP value; it writes the constant value 0 into the DSCP field. If the original packet already carried, say, DSCP 34, it would be changed down to 0, so the marking is definitely not left unchanged.

• ✗

  It sets the DSCP value to 46, which is the default for voice.

  Why it's wrong here

  DSCP 46 equates to EF (Expedited Forwarding), which is the recommended per-hop behavior for interactive voice RTP traffic, but it is not a default marking and is not the value used here. The command in question hard-codes DSCP 0, not 46. Standard default behavior for IP packets uses DSCP 0/CS0, while EF must be explicitly configured.

• ✗

  It is invalid because class-default cannot have a set action.

  Why it's wrong here

  The class-default class is a special, mandatory class in any policy-map that matches all traffic not matched by other classes, and it fully supports marking actions. There is no restriction preventing a `set dscp` action inside class-default; in fact, it is commonly used to assign a default best-effort mark. The command is valid as long as the policy-map is correctly referenced on an interface.