Policy & QoS Questions

Cisco SD-WAN architecture implements two types of data policy:
+ Centralized data policy: policy that is configured on a Cisco vSmart Controller (hence, it is centralized) and that affects data traffic being transmitted between the routers on the Cisco SD-WAN overlay network. They affect traffic flow across the entire network.
+ Localized data policy controls the flow of data traffic into and out of interfaces and interface queues on a Cisco vEdge device. It is provisioned locally on the Cisco vEdge device, using access lists. It allows you to classify traffic and map different classes to different queues. It also allows you to mirror traffic and to police the rate at which data traffic is transmitted and received.

Question 1

Explanation

In the exhibit above, the “policer ccnp” is configured to have a maximum traffic rate of 1,000,000 bits per second and a maximum burst-size limit of 15000 bytes. Traffic exceeding these rate limits is dropped.

The policer is then included in the access list “acl-guest”, which is configured to accept all TCP traffic (protocol 6) originating from the host at source 172.16.10.0/24 and going to the destination host at 172.16.20.0/24 on port 20. All other traffic is dropped (default-action-drop) -> Therefore answer C is correct (as all UDP traffic is dropped).

Reference: https://sdwan-docs.cisco.com/Product_Documentation/Software_Features/Release_18.4/08Forwarding_and_QoS/03Forwarding_and_QoS_Configuration_Examples

Question 2

Question 3

Explanation

When traffic exceeds 20 MB (configured in the policer burst command), we change the Packet Loss Priority (PLP) from low to high (configured by the policer exceed remark command).

Reference: https://sdwan-docs.cisco.com/Product_Documentation/Software_Features/Release_18.4/08Forwarding_and_QoS/03Forwarding_and_QoS_Configuration_Examples

exceed is the action to take when the burst size or traffic rate is exceeded. action can be drop (the default) or remark. The drop action is equivalent to setting the packet loss priority (PLP) bit to low. The remark action sets the PLP bit to high.

Reference: https://www.cisco.com/c/en/us/td/docs/routers/sdwan/configuration/policies/vedge/policies-book/data-policies.html

Question 4

Explanation

The “Application Aware Routing” policy is created under “Centralized Policy”.

Question 5

Question 6

Question 7

Explanation

Centralized data policy: policy that is configured on a Cisco vSmart Controller (hence, it is centralized) and that affects data traffic being transmitted between the routers on the Cisco SD-WAN overlay network. They affect traffic flow across the entire network. This will also help in controlling to send specific application traffic over specific tunnel based on jitter, delay, latency.