The components of the switch, the functions of each part, and the startup process of the switch

Hello, dear. The main functions of the switch are 1. Switch Like a hub, the exchange hall grinder provides a large number of ports for cable connection, which can be routed in a star topology. 2. The switch is like a repeater, a hub and a bridge, when it is framed, the switch will regenerate an undistorted square electrical signal.

3. Switching Calendar Machines are like bridges, and the switches use the same ** or filtering logic on each port. 4. The switch is like a bridge, the switch divides the LAN into multiple conflict domains, and each conflict domain has an independent broadband, so the bandwidth of the LAN is greatly improved. 5. In addition to the functions of bridges, hubs, and repeaters, switches also provide more advanced features such as virtual local area networks (VLANs) and higher performance.

Traditional switches are developed from bridges and belong to the second layer of OSI, that is, the data link layer equipment. It addresses based on MAC addresses, selects routes through station tables, and the establishment and maintenance of station tables is carried out automatically by the switch. Routers belong to the third layer of OSI, that is, network layer devices, which are addressed based on IP addresses and generated through routing protocols in the routing table.

When traffic enters the switch, it is written to the MAC address table based on the source MAC address and the corresponding interface in the data frame. Compare the destination MAC address in the data frame with the existing MAC address table and decide which Hu Xiaodou interface to use to make the request. If the destination MAC address cannot be found in the MAC address table, the target MAC address table is written to the upgraded interface ** (flood) in addition to the receiving interface, and if a VLAN is divided, the corresponding VLAN is flooded.

Broadcast frames and multicast frames flood directly.

Answer]: Switch: 1. Layer 2 switching front cavity machine.

Layer 2 switching technology is relatively mature, layer 2 switch is a data link layer equipment, can identify the MAC address information in the packet, according to the MAC address for **, and the Ling group and these MAC addresses and the corresponding ports are recorded in their own internal address table.

The details are as follows: (1) When the switch receives a packet from a certain port, it first reads the source MAC address in the packet header, so that it knows which port the machine with the source MAC address is connected to;

2) Then read the destination MAC address in the packet header and find the corresponding port in the address table;

3) If there is a port corresponding to the destination MAC address in the table, copy the packet directly to this port.

2. Layer 3 switches.

Layer 3 switching technology is a technology that combines routing technology and switching technology into one. After the first data flow is routed, it will generate a mapping table of MAC address and IP address, and when the same data flow passes through again, it will pass directly from Layer 2 instead of routing again according to this table, thus eliminating the delay caused by the router's routing and improving the efficiency of packet **.

Router: RouterTraditionally, routers work in the third layer of the OSI Layer 7 protocol, and their main task is to receive data packets from one-foot orange network interfaces, and decide to go to the next destination address according to the destination address contained in them. Therefore, the router first has to find its destination address in the ** routing table, and if the destination address is found, it will add the next MAC address before the frame grid of the packet, and at the same time, the TTL (Time to Live) domain of the IP packet header will also start to subtract and recalculate the checksum.

When a packet is delivered to the output port, it needs to wait sequentially before it can be delivered to the output link.

The port address table records the MAC address of the host under the port, which is automatically created after the switch is powered on, stored in RAM, and automatically maintained.

The principle of isolating collision domains is based on the port table and the decision of a switch.

2. Decision-making.

There are three actions for a switch's decision: drop, spread, and spread.

Drop: Drops when a host on the local port accesses a host on the local port and a host on the local port is known.

:When a host under a port port accesses a host under a known port.

Spread: Spreads when a host on an unknown port accesses a host on an unknown port.

Each operation should record the MAC period of the packet delivery so that it can be accessed by other hosts.