Description of the problem

In daily maintenance, we often check whether the tag identifications of the outgoing and incoming ports on the entire signal flow of an Ethernet link can allow the signal to flow smoothly, so how should we look at the outgoing and incoming ports?

Solution

1. Before explaining the details, we will first post how the various tagged ports on the Ethernet board handle data frames:

2. As shown in the following figure:

We make an EPL Ethernet link from network element A to network element B. Normally:

Ethernet board 1: port port-access vctrunk port-tagware

Ethernet board 2: port port-access vctrunk port-tagware

With this configuration, both network elements can realize the scenario where computers can directly interface without VLANs.

Wrong view: Because the port port of the A network element is access, the signal is added to the default VLAN at 1 for the incoming port ---> at 2 for the outgoing port, the signal is stripped of the default VLAN added at 1 ---> the signal goes to 3 for the incoming port because the attribute of the vctrunk port is tagware, and because the signal does not carry VLAN, all the signals are discarded at 3 at 3 is discarded.

Correct view: for an EPL link from network element A to network element B, for Ethernet board 1, the port port is the incoming port and the vctrunk port is the outgoing port. For Ethernet board 2, the vctrunk port is the ingress port and the port port is the egress port. port and vctrunk ports are whole and cannot be viewed separately as 1,2.

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