A switch connects two hosts, how do the two hosts communicate???

Let me tell you a little bit: first host 0 wants to communicate with 1, and then host 0 adds a subnet mask through its own IP and the IP of 1.

arithmetic and finds that host 1 is in a subnet with itself, then 0 can communicate directly with 1. However, when the second layer encapsulates the MAC address of 1, 0 finds that he does not know the MAC of 1 when he communicates for the first time, and then 0 will send an ARP broadcast to ask the MAC of 1, and after the switch receives the broadcast, it will associate the MAC of 0 with the interface F0 1, that is, write it to the MAC table; Then the switch looks at the MAC of the broadcast packet and finds that the purpose is Layer 2 broadcasting, so the switch floods the packet from all interfaces except 0 1. 1 will respond to 0 when it receives the broadcast, telling its mac that the packet is packet.

When passing through the switch, the switch associates MAC 1 with port F0 2. Then 0 knows the MAC of 1, and the packet can be encapsulated, and then the packet will be sent. When the packet arrives at the switch, the switch checks the MAC table, finds the corresponding port F0 2 of MAC 1, and then sends the data out of that port.

1 receives the data, and then the mac that already knows 0, directly encapsulates the data and sends it out, goes to the switch, looks up the table, and then sends it out from f0 1. This completes the communication.

For example, if host 0 starts a high-level application ping, host 0 does not know the MAC address of host 1, so it will send an ARP broadcast packet. After receiving the ARP broadcast packet, host 1 records the IP address and MAC of host 0 in its MAC address table, and responds to host 0 with its MAC

After receiving the ARP reply, host 0 records the IP and MAC of host 1 in its own MAC address table. After the ARP mapping is established, host 0 continues to add the IP address and MAC address of host 1 to the ping packet. Then hand over the ping packet to the F0 1 port of the switch.

Note: When the switch receives the ARP packet from host 0, it records the source MAC address and port F0 1 of the ARP packet in its MAC address table. Then, according to the target MAC address, which is the broadcast address of all F, it broadcasts to all ports (except the source port).

The ARP reply packet of host 1 is processed by the switch in the same way.

Assumption a

Suppose BA sends an ARP broadcast packet to the whole region in order to know the address of B.

The switch receives the broadcast for all ports** and then receives a reply from B.

The switch then saves the port number and address of B to the MAC address table.

Then it is returned to A, telling A, B's address and port.

And then the communication was established.

In the future, if A wants to continue to send packets to B, you only need to find the location of B in the MAC address table, eliminating the broadcast process.

That's storage**.

The switch will record the MAC address of the host corresponding to each port, so that the next time the packet sent to the host at this MAC address will find the port corresponding to the host.