Ошибка destination host unreachable

Do you know the most difficult part of the job of a network engineer? You are responsible for every issue related to networking in your company. Even though everything works fine, someone will come up with a complaint, and it is on our head to fix it.

While I was working as a network engineer trainee, I received a call from the development section. The manager on Duty in the development section was angry and said that the network was not working.

When I asked him about the issue, he said the Internet is just fine, but one of his teammates received an error while pinging to a device in his subnet.

His teammate received the Destination Host Unreachable reply while he tried to ping to another computer in his section.

The manager on Duty demanded an explanation for the Destination Host Unreachable. I explained to him the reasons to receive Destination Host Unreachable error messages with examples. If you have not seen this error message before, have a look at the screenshot attached below.

What Is The Reason to Receive Destination Host Unreachable Error Message?

If you want a one-sentence answer, look at the statement in the table.

Let me explain with the example I showed above. When I sent Ping packets to the IP address 192.168.225.45 from my computer, it looked at the ARP table stored in my PC to fetch the MAC address associated with the destination IP Address.

You know the basic rule of network communication. You cannot send packets to an IP Address before finding the MAC address (Physical Address) of the destination device.

ARP table shows the MAC address of the devices assigned with the specific IP Address.

If you do not know this concept, there are tons of tutorials available about Address Resolution Protocol (ARP) on the Internet.

My computer could not find the ARP Address mapped to the IP Address 192.168.225.45 in the ARP table.

C:systosys>ping 192.168.225.45

Pinging 192.168.225.45 with 32 bytes of data:
Reply from 192.168.225.47: Destination host unreachable.
Reply from 192.168.225.47: Destination host unreachable.
Reply from 192.168.225.47: Destination host unreachable.
Reply from 192.168.225.47: Destination host unreachable.

Ping statistics for 192.168.225.45:
    Packets: Sent = 4, Received = 4, Lost = 0 (0% loss),

C:systosys>Destination Host Unreachable

So it displayed Reply from 192.168.225.47: Destination host unreachable as the response.

How to Fix Destination Host Unreachable?

If you do not know how to fix the reply from the x.x.x.x destination host unreachable message, follow the instructions provided below.

1. Flush the ARP Cache

   The first step to troubleshoot the Reply from 192.168.225.47: Destination host unreachable error is by deleting all entries in the ARP table on your computer.

   • Open the Command Prompt as Administrator
     1. Type cmd on the Windows Search
     2. Right Click on the Command Prompt from the Search Window
     3. Click on the Run as Administrator option

   • Type the following command and press enter

     netsh interface ip delete arpcache

   • Try ping the same IP address again and check for the issue.
2. Run a Traceroute

   If the problem persists, you should run a traceroute to pinpoint the problem location.

   1. Open Command Prompt
   2. Type the following command and press the enter key.

      tracert 192.168.225.45

   3. Check the result to understand the reason for the Destination Host Unreachable message.

      

   Why do I receive the ping reply Destination Host Unreachable? The traceroute result shows there is no such destination device.

3. Disable the Firewall on your PC

   In my experience, some users said faulty Firewall settings caused the Destination Host Unreachable error. So, I suggest you turn off the firewall on your laptop and check for the issue.

4. Check the Status of the Destination Device and Test the Connection

   If the destination device is in your reach, make sure the device is on. Make sure the network connection is fine.

   You may unplug and replug the network cable to verify the connection status.

How to Check if Destination a Host Unreachable Error is Resolved?

It is very simple. You need to ping the same IP Address.

If the error is at the side of the IP Address, you should try to ping a different IP Address or domain name.

For example, check the command below to test whether the Destination a Host Unreachable Error fixed or not.

ping www.systosys.com

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

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

The same can be true for you too. When you troubleshoot your connectivity problems, the chances of getting this ping reply are very high.

If you learn how to resolve this error by yourself, you can fix most of your Internet connectivity problems yourself. In this tutorial, I will explain everything about this error.

By the first part, you will learn the meaning of this ping reply.

The second part of this article explains the reasons to get the ping reply Destination Host Unreachable.

You will learn how to fix the Destination Host Unreachable ping error in the last part.

What does Destination Host Unreachable Ping Reply Mean?

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

The Destination Host Unreachable error tells that the ping packets from your computer cannot find a route to the destination IP address(destination host).

Now you understand the meaning of this ping reply. However, to learn more about this error, you should ask yourself two questions.

1. Who replied to your device this Destination Host Unreachable message?
2. Why the ping packets from your computer failed to reach the destination address?

Let me answer the questions one by one. But before I explain the first question, you must learn how the ping operation works.

When you ping an address, this is how it works.

• I am pinging to my blog by typing ping www.corenetworkz.com on command prompt.
• Ping packets reach the default gateway
• Checking the ARP table and Routing table
• Finding a route to the Remote Gateway of the destination IP address
• Remote Gateway forwards the ping packets to the destination host
• Remote host reply with an acknowledgment

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. Destination Gateway

How do you know whether the reply comes from your 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. Two types of error messages are common on Windows devices.

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

   If you see the following format, check the IP address. Most of the time, X.X.X.X must be a remote gateway address. Which shows the error message you received is from the remote gateway.

2. Destination Host Unreachable

   If you don’t see an IP address in the error reply, your default gateway sends it.

Both error formats have different reasons. I will explain the reasons to get either format in the next part.

Reasons to Get the ICMP Error Destination Host Unreachable

Any 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 issue on Remote gateway
3. The destination host might be down
4. Loose Connection
5. Wrong Firewall Settings

One of the frequent questions I received from our readers is whether this error is related to the Operating System like Windows error and Linux error?

The answer is no.

Analyzing the ICMP Echo Destination Host Unreachable

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

Here 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>

Which format is this? It is the second format of the Destination Host Unreachable error. Let me explain how to resolve this error.

How to Fix Ping Error Destination Host Unreachable?

If you do not want to go into the complexity of this ICMP Echo, you can follow the instructions below to resolve the Destination Host Unreachable Ping error message.

1. Disable the firewall

   Aggressive firewall settings can cause the destination host unreachable error.

   To check whether the firewall is the reason for this issue, disable it on your computer.

   Try to access the Internet after disabling the firewall.

2. Perform a Power Cycle in your Network
   • Switch off the devices on your network
   • Disconnect power cables from Modem and Router
   • Disconnect the Ethernet cables from Modem, Computer, and Router
   • Reconnect the power and ethernet cables
   • Power on the Modem and Router after one minute
3. Disable IPv6 and Test the Connectivity

   Sometimes devices fell into the IP version conflicts. Different operating systems have different IP version priorities.

   Windows 10 prefer IPv6 to IPv4. The same is true for the major Linux variants like Ubuntu, Fedora, Debian, etc.

   However, sometimes devices fail to work properly with IPv6.

   Rarely it results in ICMP error messages. We can check it by disabling the IPv6 on your device.

   Let us check how to disable the IP Version 6 on a Windows 10 computer and test the 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.

I have two ubuntu computers on a local network and neither one of them can ping each other. Every time I try I get the «destination host unreachable» error message. Both computers are able to access the internet with any problems.

I have a ActionTech v1000h router from Telus. I’ve been in touch with one of their customer representatives and they said that there should’t be any reason why two devices cannot ping each other on the network.

I’m totally at a loss, do any of you guys have any ideas?

Computer 1:

ifconfig -a

lo        Link encap:Local Loopback  
          inet addr:127.0.0.1  Mask:255.0.0.0
          inet6 addr: ::1/128 Scope:Host
          UP LOOPBACK RUNNING  MTU:65536  Metric:1
          RX packets:10084 errors:0 dropped:0 overruns:0 frame:0
          TX packets:10084 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0 
          RX bytes:797420 (797.4 KB)  TX bytes:797420 (797.4 KB)

wlan0     Link encap:Ethernet  HWaddr c4:85:08:77:d3:f5  
          inet addr:192.168.1.77  Bcast:192.168.1.255  Mask:255.255.255.0
          inet6 addr: fe80::c685:8ff:fe77:d3f5/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:373068 errors:0 dropped:0 overruns:0 frame:0
          TX packets:380158 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:103445020 (103.4 MB)  TX bytes:112630337 (112.6 MB)

route -n

Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
0.0.0.0         192.168.1.254   0.0.0.0         UG    0      0        0 wlan0
169.254.0.0     0.0.0.0         255.255.0.0     U     1000   0        0 wlan0
192.168.1.0     0.0.0.0         255.255.255.0   U     9      0        0 wlan0

sudo iptables -L

Chain INPUT (policy ACCEPT)
target     prot opt source               destination         

Chain FORWARD (policy ACCEPT)
target     prot opt source               destination         

Chain OUTPUT (policy ACCEPT)
target     prot opt source               destination  

Computer 2:

ifconfig -a

etho0     Link encap:Ethernet HWaddr 00:24:8c:ae:f6:91
          UP BROADCAST MULTICAST MTU:1500 Metric:1
          RX packets:0 errors:0 dropped:0 overruns:0 frame:0
          TX packets:0 errors:0 dropped:0 overruns:0 carrier:2
          collisions:0 txqueuelen:1000
          RX bytes:0 (0.0 B) TX bytes:0 (0.0 B)

lo        Link encap:Local Loopback  
          inet addr:127.0.0.1  Mask:255.0.0.0
          inet6 addr: ::1/128 Scope:Host
          UP LOOPBACK RUNNING  MTU:65536  Metric:1
          RX packets:110 errors:0 dropped:0 overruns:0 frame:0
          TX packets:110 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0 
          RX bytes:8414 (8.4 KB)  TX bytes:8414 (8.4 KB)

wlan0     Link encap:Ethernet  HWaddr 00:22:43:9b:7b:64  
          inet addr:192.168.1.2  Bcast:192.168.1.255  Mask:255.255.255.0
          inet6 addr: fe80::222:43ff:fe9b:7b64/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:252 errors:0 dropped:0 overruns:0 frame:0
          TX packets:435 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:123143 (123.1 KB)  TX bytes:65828 (65.8 KB)

route -n

Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
0.0.0.0         192.168.1.254   0.0.0.0         UG    0      0        0 wlan0
192.168.1.0     0.0.0.0         255.255.255.0   U     9      0        0 wlan0

sudo iptables -L

Chain INPUT (policy ACCEPT)
target     prot opt source               destination         

Chain FORWARD (policy ACCEPT)
target     prot opt source               destination         

Chain OUTPUT (policy ACCEPT)
target     prot opt source               destination  

Edit: Example of the error when computer 1 tries to ping computer 2:

ping 192.168.1.2

PING 192.168.1.2 (192.168.1.2) 56(84) bytes of data.
From 192.168.1.77 icmp_seq=1 Destination Host Unreachable
From 192.168.1.77 icmp_seq=2 Destination Host Unreachable
From 192.168.1.77 icmp_seq=3 Destination Host Unreachable
From 192.168.1.77 icmp_seq=4 Destination Host Unreachable
From 192.168.1.77 icmp_seq=5 Destination Host Unreachable
From 192.168.1.77 icmp_seq=6 Destination Host Unreachable
^C
--- 192.168.1.2 ping statistics ---
7 packets transmitted, 0 received, +6 errors, 100% packet loss, time 6031ms
pipe 3

Edit 2: arp -a of both computers

Computer 1:

? (192.168.1.254) at 20:76:00:f5:3b:70 [ether] on wlan0

Computer 2:

? (192.168.1.254) at 20:76:00:f5:3b:70 [ether] on wlan0
? (192.168.1.77) at <incomplete> on wlan0

Edit 3: nmap -sn 192.168.1.0/24 on computer 2

Starting Nmap 6.40 ( http://nmap.org ) at 2014-05-07 21:14 PDT
Nmap scan report for 192.168.1.2
Host is up (0.00024s latency).
Nmap done: 256 IP addresses (1 host up) scanned in 3.30 seconds

Edit 4: The tcpdump logs of both computers while the first ping 192.168.1.254 and then each other:

Computer 1:

tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on wlan0, link-type EN10MB (Ethernet), capture size 65535 bytes
22:45:01.661300 ARP, Request who-has 192.168.1.2 tell 192.168.1.77, length 28
22:45:02.659393 ARP, Request who-has 192.168.1.2 tell 192.168.1.77, length 28
22:45:03.659394 ARP, Request who-has 192.168.1.2 tell 192.168.1.77, length 28
22:45:04.676872 ARP, Request who-has 192.168.1.2 tell 192.168.1.77, length 28
22:45:05.675391 ARP, Request who-has 192.168.1.2 tell 192.168.1.77, length 28
22:45:06.675396 ARP, Request who-has 192.168.1.2 tell 192.168.1.77, length 28
22:45:07.692825 ARP, Request who-has 192.168.1.2 tell 192.168.1.77, length 28
22:45:48.379058 ARP, Request who-has 192.168.1.77 tell 192.168.1.254, length 28
22:45:48.379108 ARP, Reply 192.168.1.77 is-at c4:85:08:77:d3:f5, length 28
22:45:54.419388 ARP, Request who-has 192.168.1.254 tell 192.168.1.77, length 28
22:45:54.420875 ARP, Reply 192.168.1.254 is-at 20:76:00:f5:3b:70, length 28

Computer 2:

reading from file pc2.pcap, link-type EN10MB (Ethernet)
22:44:43.538367 ARP, Request who-has 192.168.1.254 tell 192.168.1.2, length 28
22:44:43.676705 ARP, Reply 192.168.1.254 is-at 20:76:00:f5:3b:70 (oui Unknown), length 28
22:45:02.107935 ARP, Request who-has 192.168.1.254 tell 192.168.1.2, length 28
22:45:02.107951 ARP, Reply 192.168.1.254 is-at 20:76:00:f5:3b:70 (oui Unknown), length 28
22:45:06.780619 ARP, Request who-has 192.168.1.77 tell 192.168.1.2, length 28
22:45:07.778419 ARP, Request who-has 192.168.1.77 tell 192.168.1.2, length 28
22:45:08.778419 ARP, Request who-has 192.168.1.77 tell 192.168.1.2, length 28
22:45:09.796214 ARP, Request who-has 192.168.1.77 tell 192.168.1.2, length 28

Edit 5: Setup static ips for both computers etho0 and connected them with an internet cable. Both computers can definitely ping each other through the ethernet cable! ifconfig -a eth0 results:

Computer 1:

eth0      Link encap:Ethernet  HWaddr 68:68:68:00:62:a4  
          inet addr:192.168.1.10  Bcast:192.168.1.255  Mask:255.255.255.0
          inet6 addr: fe80::6a68:68ff:fe00:62a4/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:15 errors:0 dropped:0 overruns:0 frame:0
          TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:4060 (4.0 KB)  TX bytes:7629 (7.6 KB)

Computer 2:

eth0      Link encap:Ethernet  HWaddr 00:24:8c:ae:f6:91  
          inet addr:192.168.1.20  Bcast:192.168.1.255  Mask:255.255.255.0
          inet6 addr: fe80::224:8cff:feae:f691/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:250 errors:0 dropped:0 overruns:0 frame:0
          TX packets:130 errors:0 dropped:0 overruns:0 carrier:3
          collisions:0 txqueuelen:1000 
          RX bytes:26501 (26.5 KB)  TX bytes:20897 (20.8 KB)