Exam JN0-650 Topic 4 Question 44 Discussion
Actual exam question for Juniper's JN0-650 exam
Question #: 44
Topic #: 4
Question #: 44
Topic #: 4
You are configuring CoS throughout your enterprise network using DSCP. You have configured MF classification on your edge devices and are using BA classifiers throughout the core You are using the EZQoS template provided on your EX Series switches that are acting as your edge devices. You have loaded the configuration group and applied it to the appropriate interfaces. Classification and scheduling are working properly on your edge devices; however, traffic is not being classified correctly when it reaches your core devices In this scenario, which statement is correct about solving this problem?
Suggested Answer: C Vote an answer
In an end-to-end CoS (Class of Service) design, there is a clear distinction betweenclassificationat the ingress andrewrite rulesat the egress.
* The Problem:Your edge devices are successfully classifying traffic (assigning packets to internal forwarding classes). However, the core devices-which useBA (Behavior Aggregate) classifiers-are not classifying correctly. BA classifiers look at the bits in the packet header (like DSCP or 802.1p) to determine priority.
* The Missing Link (Option C):When a packet leaves the edge device, its internal forwarding class and loss priority must be "written" back into the packet header so that the next-hop (the core device) can see it. By default, Junos may not preserve or set these bits correctly on egress. You must applyrewrite rules on the edge switches' egress interfaces facing the core. These rules ensure the DSCP values in the headers match the forwarding class determined by the edge's MF classifier, allowing the core's BA classifier to function properly.
* Other Options:Option A(policer) handles rate limiting, not classification.Option Bis incorrect because core devices often have different hardware or scaling needs than edge switches, and standard BA configuration is preferred over templates in the core.Option Dis incorrect because MF classifiers are standard for edge devices where deep packet inspection is needed to identify traffic types.
* The Problem:Your edge devices are successfully classifying traffic (assigning packets to internal forwarding classes). However, the core devices-which useBA (Behavior Aggregate) classifiers-are not classifying correctly. BA classifiers look at the bits in the packet header (like DSCP or 802.1p) to determine priority.
* The Missing Link (Option C):When a packet leaves the edge device, its internal forwarding class and loss priority must be "written" back into the packet header so that the next-hop (the core device) can see it. By default, Junos may not preserve or set these bits correctly on egress. You must applyrewrite rules on the edge switches' egress interfaces facing the core. These rules ensure the DSCP values in the headers match the forwarding class determined by the edge's MF classifier, allowing the core's BA classifier to function properly.
* Other Options:Option A(policer) handles rate limiting, not classification.Option Bis incorrect because core devices often have different hardware or scaling needs than edge switches, and standard BA configuration is preferred over templates in the core.Option Dis incorrect because MF classifiers are standard for edge devices where deep packet inspection is needed to identify traffic types.
by Vito at Jul 07, 2026, 07:45 PM
0
0
0
10
Comments
Upvoting a comment with a selected answer will also increase the vote count towards that answer by one. So if you see a comment that you already agree with, you can upvote it instead of posting a new comment.
Report Comment
Commenting
You can sign-up / login (it's free).