The rules for exchanging data between computers
It is a very simple protocol used for transmission of IP datagrams across a serial line.
Serial link internet protocol..............
DATA Transmission is done through SLIP (Serial Line Internet Protocol) & PPP (Point to Point Protocol) Protocols to enable computers to interact with Internet over Telephone Line.
there may be the issue with the layer 2 protocol like hdlc or ppp is not configured or wrongly configured if the interface is serial interface.
The most likely cause for any type of line protocol being down is that a network administrator used the shutdown command on these lines to prohibit access to telnet, ssh and connection to the line con 0.
To change the line protocol from down to up, first ensure that the physical connection is intact and that the interface is enabled. You can do this by accessing the device's configuration mode (e.g., using a command-line interface) and issuing the command to enable the interface, such as no shutdown on Cisco devices. Additionally, check for any misconfigurations, link issues, or hardware failures that may be affecting the connection. Once these issues are resolved, the line protocol should come up.
IP, Enhanced Interior Gateway Routing Protocol (EIGRP), Serial Line Interface Protocol Frame Relay, Routing Information Protocol Version 2 (RIPv2),VLANs, Ethernet, access control lists (ACLs).
For CSLISP, the TCP header is reduced from about 20 characters to about 7. The actual data is not compressed, so you don't save very much in transmission costs per packet.
Ifconfig
SerialLineInternetProtocol
PPPis more secure than SLIP. PPP uses two authetication Protocols : 1. Password Authetication Protocol (PAP) 2. Challenge Handshake Authetication Protocol (CHAP) So if you use SLIP on network that unauthorized user can gain acces to.
The message is something like "Serial 0/0 is up, line protocol is down". The first part refers to the physical connection (layer 1 of the OSI model), which works in this case; the second part refers to layer 2 of the OSI model (the serial networking protocol, like HDLC or PPP), which in this example doesn't work for some reason.