Question

When is a flow categorized with QoS priority 255, even though there is no network rule to assign this priority?

Answer

QoS priority 255 is referred to as the Default priority in the BW Management window (Network > BW Management).

There are several reasons why a flow can be assigned the lowest QoS priority 255:

• Blocked/prompted flows will be categorized according to the configured network rule. If none exists, they will be categorized as P255.
• Traffic that is redirected from a block page is assigned QoS priority 255. For example, when someone tries to go to a compromised website that is blocked by IPS.
• At the destination site (WAN flows), the first packets, before the flow is identified, are assigned the lowest QoS priority 255.

The flow will get the highest priority when:

• Cato evaluates the network profile for each flow, and the QoS priority is assigned when the flow is identified with a specific application as follows:
  
  • At the source site, the first packets, before the flow is identified, are assigned the highest QoS priority.
  • Until the application behind the flow is recognized, it retains the highest QoS priority. This can be seen in the Analytics window until the application is identified.