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[All About Switches] L2PT Fails

Latest reply: Mar 8, 2018 03:49:29 1508 1 1 0 0

Involved Products and Versions

All products and versions


As shown in Figure 1-1, SwitchA, SwitchB, and SwitchC are directly connected. L2PT is configured on SwitchB. STP packets need to be transparently transmitted from SwitchA to SwitchC through SwitchB.

Figure 1-1 Networking diagram for the L2PT failure



Fault Symptom

SwitchB fails to transparently transmit STP packets.

Troubleshooting Procedure

                          Step 1     Check the configurations of the interfaces GE0/0/1 and GE0/0/2 on SwitchB.

STP packets are transparently transmitted based on VLAN 1226, but the interface GE1/0/1 does not allow packets of VLAN 1226 to pass through. Therefore, transparent transmission fails.

interface GigabitEthernet1/0/1
 port link-type hybrid
 port hybrid tagged vlan 19 21
 stp disable
 l2protocol-tunnel stp vlan 1226

interface GigabitEthernet1/0/2
 port link-type hybrid
 port hybrid tagged vlan 1226
 stp disable
 l2protocol-tunnel stp vlan 1226

Run the port hybrid tagged vlan 1226 command on the interface GE1/0/1. The fault is rectified.


Conclusions and Suggestions

When L2PT is enabled on an interface, the ID range of VLANs whose packets are allowed to pass through the interface must contain the VLAN IDs in the Layer 2 protocol packets.

  • x
  • convention:

Created Mar 8, 2018 03:49:29

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  • x
  • convention:


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