CoS Processing and Header Fields JN0-664 Practice Questions (Page 2)

Questions 6–10

1. 6foundation · easy

   In an IPv4 packet, where is the DSCP field located?

   • AIn the Ethernet header
   • BIn the MPLS shim header
   • CIn the Type of Service (ToS) byte of the IP header
   • DIn the TCP header
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2. 7application · medium

   A service provider is deploying a new MPLS-based L3VPN service. The operations team wants to ensure that voice traffic (marked with EXP 5) is forwarded to a dedicated queue and receives priority scheduling, while best-effort traffic (EXP 0) is mapped to a standard queue. The provider uses Junos CoS defaults and does not want to configure a custom classifier. Which configuration approach satisfies the requirement?

   • AConfigure a fixed classifier to assign EXP 5 to the network-control forwarding class and EXP 0 to the best-effort forwarding class.
   • BApply a policer to the interface that marks EXP 5 traffic with a higher loss priority, ensuring it is scheduled to a priority queue.
   • CApply a custom multifield classifier that matches the EXP field and assigns forwarding classes based on the configured values.
   • DUse the default behavior aggregate classifier for MPLS, which maps EXP 5 to the expedited-forwarding forwarding class and EXP 0 to the best-effort forwarding class.
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4. 8foundation · easy

   What is the role of the loss priority field in Junos CoS?

   • AIt controls the scheduling priority of the queue.
   • BIt determines which packets are dropped first during congestion.
   • CIt determines the forwarding class of the packet.
   • DIt sets the DSCP value on the outgoing packet.
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5. 9foundation · easy

   Which CoS mechanism uses the loss priority field to decide whether to drop a packet during congestion?

   • AScheduler
   • BRewrite rule
   • CPolicer
   • DDrop profile
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6. 10application · medium

   A network engineer is configuring CoS on a router that receives both IPv4 and MPLS traffic. The engineer needs to classify traffic based on the DSCP field for IPv4 packets and the EXP field for MPLS packets. Which configuration approach should be used?

   • AApply a DSCP-based BA classifier to the IPv4 interface and an EXP-based BA classifier to the MPLS interface.
   • BApply a single BA classifier that uses both DSCP and EXP fields.
   • CApply a fixed classifier that uses the incoming interface to determine the classification.
   • DApply a multifield classifier that matches both DSCP and EXP fields.
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