Reply from X.X.X.X: Destination Host Unreachable

During my network engineer career, one of the common ICMP errors I received while troubleshooting connectivity issues was Destination Host Unreachable.

This error was the cause of my Internet connectivity problems most of the time.

In this tutorial, I will explain everything about this error. I developed this tutorial in three parts.

1. The first part of this tutorial explains the meaning of the ICMP reply Destination Host Unreachable.

2. The second part explains the reasons for the ping reply Destination Host Unreachable.

3. The third part explains the steps to fix this error message.

So, let me start the tutorial developed for the fresh Network Engineers at CoreNetworkZ Tech Solutions.

Before proceeding to the core of this tutorial, let me explain the meaning of this ping reply.

The Destination Host Unreachable reply says that the ping packets from your computer couldn't find the destination device or something prevents them from reaching it.

Now that you understand the meaning of this ICMP error message. Let me answer two questions posed by two Network Engineer trainees at CoreNetworkZ Tech Solutions.

Christo Fernandes asked, "Hello Alex, I see the Destination Host Unreachable Error message, but I do not know which device is responsible for showing this ICMP reply?"

Anita Thomas, a Network Engineer Trainee at CoreNetworkZ Tech Solutions, asked, "What does my PC mean by showing this Ping reply?"

I will answer Christo and Anita. But before I answer them, you must learn how the ping test works. Then only I can explain it.

I will explain the workings of a ping test by showing a practical example. For that, I am pinging my blog by typing ping www.corenetworkz.com into the Command Prompt.

So, what will happen? Well, you can see the complete process below.

• ICMP Echo Requests travel out of my computer through the network adapter.

• Ping packets reach the default gateway. The default gateway is the router in most cases.

• The default gateway needs to find a route to the destination address. So, the next step is checking the ARP table and Routing table.

• Default Gateway finds a route to the Remote Gateway of the destination IP address.

• Remote Gateway receives the packets.

• Remote Gateway forwards the ping packets to the remote host (the final destination - server of CoreNetworkZ.com).

• The Remote Host (web server of CoreNetworkZ.com) acknowledges by sending ICMP Echo Replies.

Now, let us come back to Christo's question. Can you tell me the potential sources for a Destination Host Unreachable reply from this ping workflow algorithm?

You can get this reply from two possible sources.

1. Your Default Gateway

2. Remote Gateway

How do we know whether the reply comes from the Default Gateway or Remote Gateway?

Well, it is simple.

All you have to do is to analyze the ping reply carefully. Check the format of the message. It comes in two different forms.

1. Reply from x.x.x.x Destination Host Unreachable

   Before explaining it, let me quote a comment from one of my readers.

   Kenney Jacob, a regular reader of CoreNetworkZ Tech Solutions, asked, "Hello Alex, I see a strange response on the DOS window. It says Reply from 192.168.1.101: Destination Host Unreachable. What is it?"

   If you see the following format, check the IP address.

   Most of the time, x.x.x.x must be a Remote Gateway address.

   It shows that the error message you received was from the remote gateway.

2. Destination Host Unreachable

   If you don't see an IP address in the error replies, they came from the Default Gateway.

   In a home network, your home router is the Default Gateway.

Both error formats have different reasons. I will explain the reasons in the next part.

Let us check why your computer displays the message Reply From x.x.x.x Destination Host Unreachable.

One of the reasons listed below can get you to the ICMP Echo message Destination Host Unreachable.

1. Your Default Gateway doesn't know the route to the destination IP address.

2. Packet Routing issues on Remote Gateway.

3. The destination host might be down.

4. Loose Connection.

5. Strict Firewall Settings.

One of the frequent questions I receive from our readers is whether this error is related to Operating Systems ( like Windows and Linux ).

Lakshmi Dixit, an Engineering student, asked, "Hello Alex, I plan to install Ubuntu Linux on my Windows 11 laptop. Windows 11 frequently shows connection issues. When I ping Google, I get this reply: Reply from 192.168.100.65: Destination Host Unreachable. Is it a Windows 11 problem? Is Ubuntu free from it?"

Analyzing the ICMP Echo Destination Host Unreachable

Let me explain why I received this ICMP Echo Reply by analyzing a live example.

I send ping packets to the global DNS address 4.2.2.2 to troubleshoot the connectivity problem. The screenshot below shows the reply I received.

Microsoft Windows [Version 6.1.7600]
Copyright (c) 2009 Microsoft Corporation.  All rights reserved.

C:\corenetworkz;ping 4.2.2.2

Pinging 4.2.2.2 with 32 bytes of data:

Destination host unreachable.
Destination host unreachable.
Destination host unreachable.
Destination host unreachable.

Ping statistics for 4.2.2.2:
    Packets: Sent = 4, Received = 0, Lost = 4 (100% loss),

C:\corenetworkz>

Since you have learned the two types of this ICMP reply, let me ask you a simple question. Which format is this? It is the second format of the Destination Host Unreachable error.

It is the final part of this tutorial. Let us check how to resolve Destination Host Unreachable error on a PC.

1. Turn Off The Firewall

   According to Ashish Mudgal, a senior Network Engineer at CoreNetworkZ Tech Solutions, aggressive firewall settings can interrupt the ICMP Echo Requests and cause the Destination Host Unreachable error.

   Turn Off the Firewall to check whether the firewall is the reason for this issue on your computer.

   Try to access the Internet after the firewall is Off.

   Now, I suggest you ping a website and check whether the issue persists. If so, go to the second solution.

2. Power Cycle The Network

   A loose connection in your home network can invite the Destination Host Unreachable ICMP Echo Reply.

   
   

   Outdated Routing and ARP tables also result in Ping errors.

   
   

   A proper home network Power Cycle can fix this. Let us check the steps.

   • Switch off every device in the network.

   • Disconnect power cables from Modem, PC, and Router.

   • Disconnect the Ethernet cables from Modem, Computer, and Router.

   • Reconnect the power and ethernet cables.

   • Power On the Modem and wait for one minute.

   • Power On the Router and wait for one minute.

   • Power On the PC and ping Google to check whether the Destination Host Unreachable error persists.

   Shalini Menon, a B.Tech Computer Science and Engineering student, mentioned she could fix this issue by power cycling the home network. She asked why it fixed the problem.

   The answer is simple.

   A proper Power Cycle will fix issues like corrupted ARP and Routing tables and loose connections.

   In my experience, this solution usually resolves the issue. However, if it persists, proceed to the final solution.

3. Disable IPv6 and Test the Connectivity

   Sometimes devices fall into IP version conflicts. Different operating systems have separate IP version priorities.

   Windows 10 prefers IPv6 to IPv4. Linux variants like Ubuntu, Fedora, and Debian prefer IPv6 to IPv4.

   However, sometimes devices fail to work with IPv6.

   It results in ICMP error messages. We can check for this by turning off IPv6 on your device.

   Let's see how to disable IPv6 on a Windows 11 computer and test whether it resolves the 'Destination Host Unreachable' issue.

   • Right-click on the Network Adapter at the system tray.

   • Click on Open Network & Internet settings.

   • Click on Change Adapter options.

   • Right Click on the current connection and click properties.

   • Uncheck the Internet Protocol Version 6 (TCP/IPv6).

   • Click OK

   • Reboot your Computer.

   Once you reboot your computer, check for the connection.

Let me conclude this article now. I understand it was a long read, but you learned about a critical ICMP error: 'Destination Host Unreachable.' What do you think of my article? I welcome your questions and suggestions in the comment section.