Common Ethernet Layer 2 interface types include the following three types:
1. Access interface
Access link type port is a trunk mode of a switch. Whether a trunk connection can be established between two ports of two switches depends on the combination of these two port modes.
The Access port opens the VLAN tag after receiving the Ethernet frame, and strips the VLAN tag when forwarding the outgoing port, which is transparent to the end host, so it is usually used to connect without recognizing the 802.1Q protocol (it supports tunneling technology, which allows the service provider to communicate within the VLAN Transmit VLAN, thus retaining the customer's VLAN) devices, such as end hosts, routers, etc.
2. Trunk interface
The Trunk port of a switch is a port used to connect two switches and can transmit data of multiple VLANs. It can package the data of multiple VLANs into one frame for transmission, and at the same time restore the frame to the data of multiple VLANs at the receiving end.
Examples of Access interface and Trunk interface
3. Hybird interface
Interface example:
4. Comparison
5. Typical examples
1. How to handle when the Access port sends data frames?
A. Forward with PVID
B. Send a message with TAG
C. Replace VLAN TAG forwarding
D. Strip TAG forwarding
Answer to test question: D
Analysis of the test question: When a Tagged frame arrives at an Access interface from other interfaces of this switch, the switch will check whether the VID in the Tag of this frame is the same as the PVID: If they are the same, the Tag of the Tagged frame will be stripped, and then you will get The untagged frame is sent from the link; if it is different, the tagged frame is discarded directly. Choose D for this question.
2. The output information of a certain switch is as shown in the figure. Which of the following interfaces can forward data frames with VLAN ID 40 and does not carry tags when forwarding? ( )
A、GE0/0/2
B、GE0/0/5
C、GE0/0/3
D、GE0/0/4
Answer to test question: B
Analysis of test questions: It can be seen from the picture. The information behind vlan 40 is composed of UT: G0/0/5 TG: G0/0/1 G0/0/3 G0/0/4, where UT indicates that after receiving the data frame of vlan 40, the label is stripped and in the form of untagged Send, TG indicates that the data frame of vlan 40 is received and forwarded directly in tagged manner. Therefore the answer is choice B.
3. The configuration information of a certain port of the switch is as follows, then this port strips the VLAN TAG when sending data frames carrying which VLANs?
（ ）
interface CigabitEthernet0/0/1
port hybrid tagged vlan 2 to 3 100
port hybrid untagged vlan 4 6
A、4、6
B、1、4、5、6
C、4、5、6
D、1、4、6
Answer to test question: D
Analysis of the test question: port hybrid untagged vlan 4 6 vlan4 and vlan6 are not tagged, and vlan1 is not tagged by default.