Description of the problem

A bureau uses Huawei S5700 switches to configure one-to-many aggregation services with the N5EFS0 board of the transmission OSN3500. The S5700 side is a trunk port, and the default VLAN ID of the port is 1. Feedback from the switch side indicates that except for the VLAN ID 1 that is not passable, the other VLANs can pass normally.

Processing

1, other VLANs can communicate normally, you can rule out the problem of the binding channel on the transmission side, check the configuration of the converged Ethernet LAN service as 802.1Q, check the VLAN consideration table, there is a VLAN 1 consideration table, the settings are normal, check the access-side Ethernet leased line service, the configuration of the port exclusivity, all the VLANs can be passed, the settings are normal.

2. check the TAG attributes of the internal and external ports of the transmission aggregation station A, and the TAG attributes of the internal and external ports of the access side stations B, C, and D. Data frames carrying VLAN tags can pass through the transmission TAG attribute ports normally, and frames not carrying VLAN tags will be discarded.

3, and the switch side to confirm that the switch-side port for the trunk side (i.e., TAG attribute), the port's PVID is 1, trunk port sends a message: compare the port's PVID and the VLAN information of the message to be sent, if the two are equal, then strip the VLAN information, and then send it again, if not equal, then send it directly. Because the PVID of the port and the VLAN of the sent message are both 1, the sent message with VLAN of 1 strips the VLAN information and does not carry VLAN, but frames without VLAN tags in the TAG attribute on the transport side are discarded and therefore do not pass.

4. After the TAG attributes of the internal and external ports of the aggregation site (station A) and the access sites (B, C, and D) of transmission are all changed to HyBrid and the default VLAN ID is set to 1, the switch communicates normally.

Root cause

The switch-side port attribute is trunk port, the PVID of the port and the VLAN of the outgoing message are both 1. The outgoing message VLAN is 1 stripped of VLAN information and does not carry VLAN, but frames with the transmission-side TAG attribute without VLAN tags are dropped and therefore do not pass.

Solution

1. On the transmission side, set the TAG attributes of both internal and external ports to HyBrid, with the default VLAN ID of 1, and passthrough the data of the switch with and without VLANs.

2. The switch side sets the PVID of the port to be inconsistent with the service VLAN to ensure that the outgoing messages all carry VLAN IDs.

Recommendation and Summary

I. Switch interface in/out data processing process:

1. Acess port receives telegrams.

Receive a message, determine whether there is VLAN information: if not, then hit the PVID of the port and exchange and forward, if there is, then directly discarded (default).

2、Acess port sends a message:

Strip the VLAN information from the message and send it out directly.

3、trunk port receives the telegram:

Receive a message, determine whether there is VLAN information: if not, type the PVID of the port and exchange and forward it, if so, determine whether the trunk port allows the data of the VLAN to enter: if it can, then forward it, otherwise discard it.

4. trunk port sends the message:

Compare the PVID of the port and the VLAN information of the message to be sent, if both of them are equal, then strip the VLAN information and send it again, if not, then send it directly.

5、hybrid port receives the message:

Receive a message, determine whether there is VLAN information: if not, then hit the port's PVID, and exchange and forward, if there is, then determine whether the hybrid port allows the data of the VLAN to enter: if it can be forwarded, otherwise discarded (at this time, the untag configuration on the port does not need to be considered, the untag configuration is only useful for sending messages).

6. the hybrid port sends the message:

1. Determine the attributes of the VLAN on the port (disp interface that is, you can see which VLANs are untagged and which VLANs are tagged on the port).

If it is untag, then strip the VLAN information and send it again, if it is tag, then send it directly.

Second, transmission side port TAG data processing:

1. Acess port receives telegrams.

Receive a message, determine whether there is VLAN information: if not, then hit the port default VLAN for forwarding, if there is directly discarded.

2、Acess port sends a message:

Strip the VLAN information from the message and send it out directly.

3. TAG port receives the telegram:

Receive a message and determine whether there is VLAN information: if not, discard it, if yes, pass it through.

4、TAG port sends a telegram: directly carry out the transmission.

5、hybrid port receives telegrams:

Frames carrying VLAN tags are directly transmitted; frames not carrying VLAN tags are forwarded with the default VLAN of the port.

6、hybrid port sends telegrams:

If the VLAN ID in the data frame is "Default VLAN ID", strip the VLAN tag and send it. If the VLAN ID in the data frame is not the "Default VLAN ID", pass through.

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