Shulou(Shulou.com)11/24 Report--

There are many layers in the communication network, and several interconnected devices at each level often appear in chat, including bridges, switches, routers, gateways and so on.

These common interconnected devices work at the network level that they are good at:

ISO/OSITCP/IP

Network equipment

Transport layer and above-high-level transport layer and application layer-high-level

Gateway

3-Network layer 2-Network layer

Router, layer 3 switch

2-data Link layer 1-Network Interface layer

Bridge (bridge), switch

1-physical layer repeaters and hubs this time let's take a look at the interconnected devices in the intermediate data link layer (layer 2) and the network layer (layer 3), and what's the difference.

Data link layer (layer 2) Data Link Layer bridge (bridge) bridge (Bridge) works at the data link layer, connects two LAN (local area networks) and forwards frames according to the MAC address.

The bridge operates in the MAC sublayer of the link layer and has the MAC address learning function to avoid broadcasting all frames.

Generally speaking, in a multi-terminal interconnected continent, there is a bridge on the road of local area network communication, but it only allows data that matches the destination MAC address to cross the bridge.

In this way, different network segments will not affect each other's work.

Tips

MAC address is used to uniquely mark a network card in the network. If a device has one or more network cards, each network card needs and will have a unique MAC address.

Switch switch (Switch) means "switch" is a kind of network device used for electrical (optical) signal forwarding, which can provide a unique electrical signal path for any two network nodes of the access switch. The most common switch is Ethernet switch, and the others are telephone voice switch, fiber optic switch and so on.

The switch can distinguish the source MAC address from the destination MAC address in the frame, so it can establish a connection between any two ports and establish a temporary switching path between the originator and the destination receiver of the data frame, so that the data frame can directly reach the destination address from the source address.

In fact, it can be understood that the switch received a request from a mother to help her bring a message to her daughter B at school.

The switch took the loudspeaker of the radio station and shouted, "B, your mother is looking for you. Please reply me when you get it!"

B just told the switch which class I was in and where I was sitting, and the switch told her mother that the message had been brought to her daughter.

The next time the mother needs to bring a message to her daughter B, the switch can go directly to B to tell her that there is no need to shout loudly.

Generally speaking, switches need to establish a MAC table to communicate with each other.

Network layer (layer 3) Network Layer router router (Router) is a hardware device that connects two or more networks. It is a dedicated intelligent network device that reads the address in each packet and then decides how to transmit it. Its function is: broadcast and multicast control, addressing data, choosing the best way to reach the destination network, traffic management, connecting to the wide area network (WAN).

Unlike a switch shouting with a loudspeaker, a router is like a courier when you want to send a delivery to a friend in Beijing (another terminal).

First of all, you need to wrap it and fill in the sender and recipient information (encapsulating the data message with the other party's IP address).

Then give the delivery to the courier (router).

In the end, the courier will transfer according to the arrangement of the express company (choose the route according to IP and routing table) and deliver the delivery to your friend.

Therefore, the router connection device mainly depends on the IP and routing table for path selection.

Layer 3 switch (Layer 3 Switch) can also forward data at the network layer by introducing routing functions. Its main purpose is to speed up the data exchange within a large local area network.

It is not too much to describe the role of layer 3 switches in many network equipment as "mainstay". There are opportunities for layer 3 switches to give full play to their abilities in campus networks and metro education networks. The core backbone network must use layer 3 switches, otherwise thousands of computers in the entire network are in a subnet, not only there is no security to speak of, but also can not isolate the broadcast storm because the broadcast domain can not be divided.

In the classroom, the two boys especially liked the class girl sitting behind them, so they kept looking at her. suddenly, the class girl stood up and was ready to go, and slipped a small rolled-up note to the boy sitting beside them as she passed them.

The boy opened the note to see what was written inside (unencapsulated up) and found that it said, "Please pass the note to the next person." The same is true of layer 3 switches. Only when it is seen that the original destination IP address is not itself, then the forwarding at the routing level is performed.

Therefore, whether the switch is performing layer 3 forwarding or not is that while the destination MAC is itself, whether the IP address is itself or not, and if it is itself, then there is no need to forward anything.

The difference between devices Distinction there are more or less similarities between several interconnected devices. Here, the switch is used as the comparison item, and the differences between the properties of the devices are distinguished in the form of tables.

Switches and routers

The most difficult to distinguish may be the switch and the router, and there are actually many differences between them.

Attribute switch

Router

Port

More and less

Interface

Default belongs to the data link layer (layer 2)

Belongs to the network layer (layer 3)

Forwarding maintenance

Maintain MAC address table according to MAC address forwarding

Maintain routing table based on IP address forwarding

Broadcast

Forwarding

Isolation

Firewall function

Unrealizable, achievable.

NAT (network address) translation is not supported

Support

Main action position

Between LAN-WAN (Local area Network-wide area Network)

Between WAN-WAN

Work level

For layer 2 and layer 3 switches

For layer 3 Devic

Network segment

Same network segment

Different network segments

Function

Weak, but fast and cheap, without dialing function

Strong, but slow and expensive, internal dial-up switches and layer 3 switches can be realized.

Layer 3 switch

Work level

Data link layer

Network layer

Use of technology

Layer 2 switching technology

Layer 2 switching technology + layer 3 forwarding technology

Function

Data forwarding

With expandability, security mechanism and billing function

The basic functions of switch and bridge switch are the same as those of bridge, which have the functions of frame forwarding, frame filtering and spanning tree algorithm. However, there are still differences between switch and bridge.

Attribute switch

Network bridge

Port

Multiple ports work simultaneously

Two ports working

Divide physical network segments

More.

Limited

Transmission rate

Faster than the bridge

Slower than the switch

Data frame forwarding mode

Direct forwarding does not require full reception

Forward after receiving complete

Tens of millions of knowledge of computer network, today's popular science is over, I believe you have some understanding of these interconnected devices in your heart, and I hope you can apply what you know today to your daily life.

This article comes from the official account of Wechat: ZTE documents (ID:ztedoc)

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