Many friends have been asking about the specific role of several ports of the switch. This is really easy for many of our friends to ignore, so let's take a look at this aspect today.
Ethernet ports have three types of links: access, trunk, hybird
Access type port: can only belong to 1 VLAN, generally used to connect to a computer port;
Trunk port: It can allow multiple VLANs to pass through and can receive and send multiple VLAN packets. It is generally used for interfaces related to switches and switches.
Hybrid port: Allows multiple VLANs to pass through. It can receive and send multiple VLAN packets. It can be used for connecting between switches and connecting to user computers.
First, the types of switches are divided. The switches are divided into low-end (SOHO-class) and high-end (enterprise).
The important difference between the two is that each physical port of the low-end switch is a logical port, and the high-end switch is configured by bundling multiple physical ports into one logical port.
E.g
In the Cisco network, there are four types of interfaces that are finally stable in the LAN: access/trunk/multi/ dot1q-tunnel.
1. access: Mainly used to access terminal devices, such as PCs, servers, print servers, etc.
2, trunk: mainly used to connect other switches, so as to carry multiple vlan on the line.
3. multi: Multiple vlans are carried in one line, but unlike trunk, it does not tag the data carried. It is mainly used to access servers supporting multiple vlans or some network analysis devices. Basically, such interfaces are not used at present, and in the network devices of cisco, such interfaces are basically not supported.
4, dot1q-tunnel: Used in the Q-in-Q tunnel configuration.
What is the link type?
The link type of vlan can be divided into access link and trunk link.
1. The access link refers to the link from the switch to the user equipment, that is, the access to the user, which can be understood as the link from the switch to the user. Since most computers cannot send frames with vlan tags, this link can be understood as a link without a vlan tag.
2. The trunk link refers to the link of the switch to the upper layer device such as the router, which can be understood as the link to the wide area network. This link usually has a vlan tag because it depends on vlan to distinguish users or services.
What is a port type?
The port types were mainly divided into two types in the past, and basically two ports, access and trunk, are used.
1. Access port: It is a port used on the switch to connect to the user's computer and is only used for access links. For example, when a port belongs to vlan 10, the data frame with vlan 10 will be sent to the port of the switch. When the data frame passes through this port, the vlan 10 tag will be stripped off and reach the user's computer. It is an Ethernet frame. When the user computer sends an Ethernet frame, go up through this port, then the port will add a vlan 10 tag to the frame. Frames of other vlan tags cannot be sent from this port to the computer.
2. trunk port: This port is the communication port between switches or between the switch and the upper device, used for trunk links. A trunk port can have a primary vlan and multiple secondary vlans. This concept can be understood as an example: for example, when a trunk port has a primary vlan 10 and multiple secondary vlan 11, 12, 30, data with vlan 30 Frames can pass through this port, vlan 30 is not stripped when passing, and can pass when the data frame with vlan 10 passes through this port. If a data frame without vlan passes, then the port will be tagged with vlan 10 tag. The existence of such a port is for the transmission of multiple vlans across switches.
It can also be seen that these two link modes correspond to the two port modes, which is not difficult to understand. The principle is understood, when you see the switch, the configuration is fully understood several times.
Access and truck mainly distinguish the port type of the switch in the VLAN
The truck port is a VLAN aggregation port connected to other switch ports. The access port is the port that the switch connects to the host in the VLAN domain.
The trunk is generally tagged. Generally, only the vlan that marked the tag is allowed to pass, so the port can allow multiple VLAN tags to pass through, and the access port is generally an untag unmarked port, and an access vlan The port only allows one access vlan to pass.
Access, trunk, and hybid are three port attributes;
A port with access can only belong to one vlan, and the port does not tag;
A port with a trunk nature can belong to multiple vlans, and the port is tagged;
A port with a hybid nature can belong to multiple vlans. Whether the port is tagged in the vlan depends on the specific situation.
Understanding of three port modes of Access, Access, Hybrid and Trunk
The port has three modes: access, hybrid, trunk. A port of the access nature can belong to only one vlan, and the port does not tag. The trunk can belong to multiple vlans, and can receive and send multiple vlan packets, which are generally used for connections between switches. Hybrid can also belong to multiple ports. Vlan, which can receive and send multiple vlan packets, which can be used for connections between switches and for connections between switches and user computers. The difference between the trunk and the hybrid is that the hybrid port can allow packets of multiple VLANs to be unlabeled, and the trunk port can only allow packets of the default VLAN to be unlabeled. The hybrid and trunk cannot coexist on the same switch.
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