Allied Telesis Layer 3 Switches manual Using QoS policy-based storm protection

Using QoS policy-based storm protection

Policy-based storm protection lets you specify one of a range of actions for the switch to take when it detects a broadcast storm. It is a part of the QoS functionality.

Policy-based storm protection is more powerful than simple bandwidth limiting. It lets you restrict storm damage to within the storming VLAN, and it gives you the flexibility to define what traffic rate makes a broadcast storm.

Configuration To use storm protection:

Protecting the network

Products

AT-8948

x900-48 Series

AT-9900 Series

AT-9924Ts

x900-24 Series

Software Versions

2.8.1 and later

1.Turn on the switch enhanced mode qoscounters, unless it is already enabled. After this, you need to restart the switch.

2.Create a classifier to match the desired traffic. To match all broadcast packets specify a destination MAC address of ff-ff-ff-ff-ff-ff.

3.Create a QoS traffic class and define the following storm protection settings in it:

z Window (stormwindow) specifies how often the switch measures traffic to decide whether to activate storm protection (in seconds).

z Rate (stormrate) specifies the amount of traffic per second that must be exceeded before the switch takes action.

z Action (stormaction) specifies what the switch does when it detects a storm: Link Down (linkdown) makes the switch physically disable the port on which the storm is occurring, so that the link goes down.

Port Disable (portdisable) makes the switch logically disable the port on which the storm is occurring, leaving the link up.

VLAN Disable (vlandisable) makes the switch block traffic only on the VLAN on which the storm is occurring.

z Timeout (stormtimeout) specifies the number of seconds that the port remains disabled for.

4.Create the rest of the QoS framework: a flow group and policy. Add the classifier to the flow group, the flow group to the traffic class, and the traffic class to the policy.

5.Apply the policy—and therefore the storm protection—to one or more ports.

The procedure above applies storm protection to classified traffic, and uses a classifier to select all broadcast traffic. This is the most common approach. If you want to, you can instead classify to select important non-broadcast traffic and apply storm protection to unmatched traffic. Unimportant or unwanted unicast and multicast traffic then counts towards the storm calculations.

To apply storm protection to unclassified traffic, configure storm protection on the default traffic class in the QoS policy settings. Use the parameters dtcstormwindow, dtcstormrate, dtcstormaction, and dtcstormtimeout.

Create A Secure Network With Allied Telesis Managed Layer 3 Switches 5