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Serverspace Black Friday
Daniil Fedorov
May 24, 2024
Updated May 24, 2024


What is ICMP

ICMP (Internet Control Message Protocol) is a network protocol designed to exchange diagnostic and error messages on IP networks. ICMP is an important component of the IP protocol and is used to control network devices and troubleshoot network problems.

Functions and features of ICMP

  1. Transmit Error Messages: ICMP is used to send error messages that may occur when transmitting IP packets. For example, if a router is unable to deliver a packet to a specified address, it can send an error message to the sender via ICMP.
  2. Transmitting diagnostic messages: ICMP is also important for diagnosing network connections. One of the best known uses of ICMP is the ping command, which can be used to check the availability of a remote host and measure the signal delay.
  3. ICMP packet structure: ICMP packets consist of a header and the body of the message. The header includes the message type, message code, and checksum. The main message content may include additional information depending on the specific message type.
  4. Different types of ICMP messages: There are many types of ICMP messages such as:
    - Echo Request and Echo Reply: These are used to check the availability of a host (for example, using the ping command).
    - Destination Unreachable: Notifies the sender that the packet cannot be delivered to the specified destination.
    - Time Exceeded: Notifies the sender that the packet's time to live (TTL) has expired.
    - Redirect: Indicates to the sender a more optimal route for sending packets.

ICMP applications and tools

  • Ping - is one of the most popular ICMP applications. It allows administrators to check host availability and measure the latency of data transmission.
  • Traceroute - uses ICMP Time Exceeded messages to determine the path that packets take through the network to the destination host. Serverspace has an article Traceroute – network tracing in Linux, which explains how traceroute works and how to install it on Linux.

Advantages of ICMP

  • Network Diagnostics: ICMP allows network administrators to identify and troubleshoot connectivity and network performance problems.
  • Network management: ICMP can be used with routing and error reporting to improve network performance.
  • Simplicity: ICMP is a simple and lightweight protocol that can be easily integrated i

Disadvantages of ICMP

  • Insecurity: ICMP can be used by attackers to launch attacks such as DoS (Denial of Service) and DDoS (Distributed Denial of Service), so ICMP requests are often restricted or filtered on networks.
  • Limited functionality: ICMP is mainly for diagnostics and error reporting and is not intended for data transmission.


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