[Transport layer, application layer]
[Transport layer]
Function: The IP layer provides point-to-point connections, and the transport layer provides end-to-end connections.
TCP protocol: Transmission Control Protocol, reliable, connection-oriented, and inefficient.
UDP Protocol: User Datagram Protocol, unreliable, connectionless, and efficient.
The TCP encapsulation format is 20 bits, and the UDP encapsulation format is 8 bits.
FIN: Disconnect.
SYN: Request a connection.
RST: Reconnect.
PSH: Provides services to the application layer.
ACK: Acknowledgement.
URG: Controls the emergency clock.
timer:
retransmission timer
keepalive timer
persist timer: zero window deadlock, wait state.
time waiting timer
——TCP protocol application——
21 FTP file transfer protocol, used for uploading and downloading.
25 SMTP Simple Mail Transfer Protocol.
53 DNS Domain name resolution, resolves network addresses to IP addresses.
80 HTTP Hypertext Transfer Protocol.
23 Telnet remote management login target host.
-- UDP protocol application --
53 DNS Domain name resolution, resolve network address to IP address.
69 TFTP Trivial File Transfer Protocol.
111 RPC remote procedure call.
123 NTP Network Time Protocol.
【Application layer】
Function: Work with applications to exchange application-specific data using the underlying network.
——Application layer protocol application——
21 FTP file transfer protocol, used for uploading and downloading.
69 TFTP Trivial File Transfer Protocol.
25 SMTP Simple Mail Transfer Protocol, send and receive mail.
110 POP3 Post Office Protocol version 3, the client receives mail.
53 DNS Domain Name Resolution Protocol.
80 HTTP Hypertext Transfer Protocol.
443 HTTPS Secure Hypertext Transfer Protocol.
23 Telnet remote management login target host.
——Telnet remote management——
Premise setting: Set management IP, console password.
Switch: (any VLAN interface)
Switch(config)# int v 1
Switch(config-if)# ip address 192.168.1.1 255.255.255.0
Configure remote management IP address
Router: (any network interface)
Route(config)# int f 0/1
Route(config-if)# ip address 192.168.1.1 255.255.255.0
Switch(config-line)# line vty 0 4 represents 01234, while allowing 5 remote management terminals
Route(config-line)# line vty 0 4 stands for 01234, allowing 5 remote management terminals at the same time
Configure the remote management IP address
Computer
Start-->Run-->cmd
to execute: telnet <target host IP address> [port number 23] Remote management host
ip routing The Layer 3 switch enables the routing function.
----telnet 192.168.1.1 192.168.1.254 routing