In order to realize VLAN data transmission between switches, switch ports are divided into three types: access, trunk and hybrid

Port type access

One access port

1.1 when the port receives data (i.e. the data enters the switch)

(1) If there is no VLAN tag on the data, the VLAN ID of the access port will be marked and the data will continue to be forwarded

(2) If there is VLAN tag in the data, it will be discarded by default regardless of whether it is consistent with the VLAN of the access port (there may be differences between different brands and different versions of the same brand; if it is consistent with the VLAN of the access port, it may be received)

1.2 port sends data (i.e. data flows out of the switch)

When the VLAN tag in the data frame is consistent with the native VLAN of the port, the VLAN tag in the data frame is removed and sent directly

(because the data frames sent by the access port are generally sent to the terminal PC, the network card of the PC can’t recognize the VLAN tag. In addition, they are sent to the access port in another same VLAN. The access port does not receive the data frames with VLAN tag by default, so the data frames sent by the access port are all without VLAN tag.)

Port type trunk

Second trunk

2.1 port receives data (i.e. data enters the switch)

(1) If the data has no VLAN tag, put on the native VLAN tag of the port and enter the port

(2) If there is VLAN tag in the data and forwarding is allowed, it will enter, otherwise it will be discarded

2.2 port sends data (i.e. data flows out of the switch)

If the VLAN tag in the packet is consistent with the native VLAN in the trunk port, the VLAN tag information will be removed and sent. If it is inconsistent but forwarding is allowed, it will be forwarded directly, otherwise it will be discarded.

Port type hybrid

3.1 port receiving data

(1) If the data is not marked with VLAN, it is labeled with native VLAN for forwarding.

(2) If the VLAN tag is carried in the data, judge whether it is allowed to forward. If it is allowed, do not modify the VLAN tag and forward, otherwise it will be discarded.

3.2 port to send data.

See whether the VLAN data needs to be labeled or not during configuration

(1) If there is no need to tag, the sending mode is the same as the access port, and the VLAN tag is removed for forwarding.

(2) If you need to tag, if the VLAN information is consistent with the native VLAN, remove the VLAN tag and grab it. If the VLAN information is inconsistent with the native VLAN, forward it as it is.

DTP Technology

Editor: hfy

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