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Configuring Layer 2 Protocol Tunneling

Tunneled Layer 2 PDUs do not normally arrive at high rate. If the tunneled Layer 2 PDUs do arrive at high rate, there might be a problem in the network. Typically, you would want to shut down the interface that is receiving a high rate of tunneled Layer 2 PDUs so that the problem can be isolated. You do so using the shutdown-threshold statement. However, if you do not want to completely shut down the interface, you can configure the switch to drop tunneled Layer 2 PDUs that exceed a certain threshold using the drop-threshold statement.

L2PT processing is done by the CPU, and L2PT traffic to the CPU is rate-limited to a maximum of 1000 pps. If traffic is received at a rate faster than this limit, the rate limit causes the traffic to be dropped before it hits the threshold and the dropped packets are not reported in L2PT statistics. This can also occur if you configure a drop threshold that is less than 1000 pps but traffic is received at a faster rate. For example, if you configure a drop threshold of 900 pps and the VLAN receives traffic at rate of 1100 pps, L2PT statistics will show that 100 packets were dropped. The 100 packets dropped because of the rate limit will not be reported. Similarly, if you do not configure a drop threshold and the VLAN receives traffic at rate of 1100 pps, the 100 packets dropped because of the rate limit are not reported.

There are no default settings for drop-threshold and shutdown-threshold. If you do not specify these thresholds, then no thresholds are enforced. As a result, the switch tunnels all Layer 2 PDUs regardless of the speed at which they are received, although the number of packets tunneled per second might be limited by other factors.

You can specify a drop threshold value without specifying a shutdown threshold value, and you can specify a shutdown threshold value without specifying a drop threshold value. If you specify both threshold values, then the drop threshold value must be less than or equal to the shutdown threshold value. If the drop threshold value is greater than the shutdown threshold value and you try to commit the configuration, the commit operation fails.

Note: L2PT and VLAN translation configured with the mapping statement cannot both be configured on the same switch.

Note: If the switch receives untagged Layer 2 control PDUs to be tunneled, then you must configure the switch to map untagged (native) packets to an L2PT-enabled VLAN. Otherwise, the untagged Layer 2 control PDU packets are discarded. For more information, see Understanding Q-in-Q Tunneling and VLAN Translation.

1. Because L2PT operates under the Q-in-Q tunneling configuration, you must enable Q-in-Q tunneling before you can configure L2PT. Enable Q-in-Q tunneling on VLAN customer-1:
   [edit]
user@switch# set vlans customer-1 dot1q-tunneling
2. Enable L2PT for the Layer 2 protocol you want to tunnel, on the VLAN:
   • To enable L2PT for a specific protocol (here, STP):
     [edit]
user@switch# set vlans customer-1 dot1q-tunneling layer2-protocol-tunneling stp
   • To enable L2PT for all supported protocols:
     [edit]
user@switch# set vlans customer-1 dot1q-tunneling layer2-protocol-tunneling all
3. (Optional) Configure the drop threshold:

   Note: If you also configure the shutdown threshold, ensure that you configure the drop threshold value to be less than or equal to the shutdown threshold value. If the drop threshold value is greater than the shutdown threshold value and you to try to commit the configuration changes, the commit operation fails.

   [edit]
user@switch# set vlans customer-1 dot1q-tunneling layer2–protocol-tunneling stp drop-threshold 50
4. (Optional) Configure the shutdown threshold:

   Note: If you also configure the drop threshold, ensure that you configure the shutdown threshold value to be greater than or equal to the drop threshold value. If the shutdown threshold value is less than the drop threshold value and you to try to commit the configuration changes, the commit operation fails.

   [edit]
user@switch# set vlans customer-1 dot1q-tunneling layer2–protocol-tunneling stp shutdown-threshold 100

   Note: Once an interface is disabled, you must explicitly reenable it using the clear ethernet-switching layer2-protocol-tunneling error command. Otherwise, the interface remains disabled.