Understanding ICMP Echo Request


Every community administrator or supervisor must perceive what ICMP or Internet Control Message Protocol is. Although that is continuously a misunderstood protocol, ICMP wisdom is useful if you wish to perceive routing. Among the core ideas of this protocol that you simply must perceive are ICMP echo request and echo answer.

Also referred to as ping packets, ICMP echo requests are despatched or won the usage of the ping command. An ICMP echo request continuously implies that the host to which the message is addressed must answer without delay to the packet the usage of an echo answer.

Normally, an echo request continuously features a set of information that you’ll specify the usage of the ping command. When a bunch makes an echo answer, all of the information within the ICMP echo request might be despatched again.

The ping command supplies the customers with all of the modalities of sending the ICMP echo requests and ICMP echo replies. Among the specs that you’ll have to make are the supply and the vacation spot addresses. Besides, you’re going to additionally want to set the opposite modalities within the IP Header phase.

When to Use Echo Request and Echo Reply Messages

Notably, each time the fundamental connectivity operations fail, one of the crucial elementary assessments that the customers choose to accomplish is to make sure if the far off device hooked up to their shopper machines is up and working. This is the place the ICMP question messages come into play. These messages are important equipment for community trying out and troubleshooting packages.

The consumer sends an ICMP Echo Request message to the far off vacation spot device, with the device replying with an ICMP Echo Reply message to ship the comments. According to RFC 1122, every host will have to enforce the ICMP Echo server, making this provider obligatory.

While this sounds lovely easy, this will likely every so often now not occur routinely. Firewalls, continuously to be had for safety causes, can block the packets. Besides, there may be the failure of packet deliveries for more than a few causes.

Again, consistent with RFC 1122, all hosts must enterprise to have an end-user-accessible app interface designated for sending Echo Request messages to every other hosts inside the community. This interface is known as ping or the ping command and must be found in all computing environments with a TCP/IP stack together with essentially the most elementary fashions.

How to Use ICMP Echo Request and Echo Reply Query Messages

Also already indicated, the ICMP (Request and Reply) Echo messages are perfect for community connectivity trying out. They will also be used for community troubleshooting functions.

Using the ping command, you’ll check the Layer 3 community connections between the host pc and every other host instrument. The host generates and sends an Echo Request message. The pc or instrument that the host despatched an Echo question message to receives the request, procedure it, and ship again an ICMP Echo Reply to the host.

In the former representation, the primary arrow displays an ICMP Echo Request (Type-8 Code-0) whilst the second one arrow indicates an Echo Reply, continuously Type-0 Code-0. An ICMP Echo Reply Message continuously signifies the Type, Code, Checksum, ID, and Sequence.

The Identifier (ID) and Sequence attributes for ICMP messages lend a hand to check the Echo Request messages with their respective Echo Reply messages. The information payload for Echo Request packets, which can be in ASCII characters, are perfect for padding. Besides, every Echo answer message will have to include the similar information payload specs as its corresponding Echo Request.

Sending an ICMP Echo Message

You can ship an Echo Request the usage of the next ping command, wherein the IP deal with is the gadget that you’re making plans to ping.

Your host gadget creates an echo message and sends it to the required instrument. The instrument will, in go back, create an echo answer and sends it again to the soliciting for host.


The ICMP command is acceptable in an array of community control purposes. While this text involved in ICMP echo request and answer question messages, it additionally is useful for troubleshooting functions.

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