In this post, let’s look at Cisco 9800 QoS in high level. Cisco 9800 (IOS-XE based controllers) support Modular QoS CLI (MQC) contrast to AireOS based WLC QoS that we discussed last post. MQC mean you require to configure class-maps, policy-maps & apply those policy-maps using service policy. When you apply QoS in 9800, 3 QoS policy target available.

  1. Port level
  2. SSID level (Metal QoS or user-defined policy)
  3. Client level (using AAA override)

9800 use a different configuration model (compare to AireOS WLC) . Each AP require to have 3 tags (policy, site & RF).

When it comes to QoS policy, it will configure under “Policy Profile” which maps into “Policy Tag“. Any AP specific configurations will be under “AP Join Profile”. Hence if you want AP to trust DSCP value of upstream traffic, that configuration will within “AP Join Profile

There are 3 options available when it comes to QoS policy configuration under “Policy Profile“.

  1. Leave it to Default settings (Platinum QoS equivalent)
  2. Configure AutoQoS
  3. Configure Custom QoS policy

Below shows the QoS policy configurations options under Configurations > Tags & Profile > Policy.

Here is the “AP Join Profile” configuration to trust upstream DSCP. This is enabled by default since IOS-XE 17.3.4 versions onward.

If we leave default configuration, let’s see what’s going to happen from QoS point of view. There won’t be any SSID level QoS policies. 9800 will trust whatever the DSCP values coming on wireless packets. Only drawback is there is no way to remark traffic to give them priority as you want (eg if MS-Team traffic comes with DSCP 0, that will go as DSCP 0 traffic to rest of network. With a QoS policy you can remark it as AF41 or any other DSCP that your require)

If you apply SSID level policy, for example metal QoS profile Gold, you will notice that influences DSCP marking of the original packet as well as the outer IP header DSCP in CAPWAP between WLC & AP

When you need to configure QoS policies, there are two choices. AutoQoS may be simple to configure, but you need to understand what granularity it gives and which applications will be in class-maps. Defining your own QoS policy may be the best approach.

  1. Use Auto QoS
  2. Define custom QoS policy

Let’s look at those in future posts.

If you are interested to learn about these 9800 QoS configurations, I am doing a Webinar 3PM CST tomorrow (30th Sep), please register using this link.

1. QoS for WLAN Professionals
2. RFC8325 – QoS Mappings
3. AireOS QoS Recommendations
4. Understanding Wireless QoS (Part 1-5)
5. 3850 QoS (Part 1-5)
6. Best Practice QoS Config (AireOS 7.x)