QoS - LLQ applied only outbound

When applying QoS queuing mechanisms such as LLQ, note that they can be applied only in an outbound direction. This is because you can only control how traffic leaves your network, not how it enters. Indeed, if you attempt to apply LLQ inbound, you will get an error message similar to this:

-POLICY_INST_FAILED: Service policy installation failed on GigabitEthernet1. service-policy not applicable for interface features. policy:test_app, dir:IN, ptype:, ctype:DEFAULT

This error may be seen because Cisco IOS/IOS-XE does not support applying service policies with the priority command (used for LLQ) in the inbound direction.

As mentioned before, for ingress traffic, network devices generally do not have control over the rate at which packets arrive. Therefore, queuing, such as LLQ, as well as shaping, which involves delaying and scheduling packets, isn’t feasible for incoming traffic.

Instead, policing can be used inbound to either drop or mark packets that exceed the defined bandwidth profile.