In this section, the focus is on diagnosing network connectivity issues using ICMP (Internet Control Message Protocol) and the "ping" command. Here's a breakdown of the information provided:

Diagnosing Network Connectivity Issues:

• Network problems often involve the inability to establish connections.
• ICMP (Internet Control Message Protocol) is used to communicate network errors between devices.
• ICMP helps routers and hosts communicate why transmissions have failed back to the origin of the transmission.

ICMP Packet Structure:

• ICMP packet consists of a header and a data section.

• Header includes fields like type, code, and checksum.
• Data payload section in an ICMP packet helps identify the transmission causing the error.

Ping Command:

• The "ping" command is a useful tool to diagnose network connectivity.
• Ping sends an ICMP echo request message to check if a destination is reachable.
• If the destination is up and running, it responds with an ICMP echo reply.
• Ping is available on most operating systems.

Using the Ping Command:

• Invoke the ping command from the command line followed by the destination IP or domain name.
• Output displays information about round-trip communications, TTL, message size, and statistics.
• On Linux and macOS, ping runs until interrupted by pressing Control + C.