Destination host unreachable in Cisco packet tracer
Many times we encountered with destination host unreachable error when creating network topologies in packet tracer.
This error can also occur in case of hardware failures or faults however that is not so common.
As packet tracer is a simulation so we cannot have hardware failures in it so most of the time, this error is observed in packet tracer due to the following reasons.
Reason 1
Pinging IP address that does not exist on the network
Many times while testing our network, we mistype the commands and IP addresses so In case if we have mistyped the IP address that does not exist in our network will cause the Destination host unreachable error.
Fix – Make sure you have typed the destination IP correctly while pinging.
Reason 2
The router does not have an entry in the routing table
If the destination IP is on the other network then the router should have the information about that network in its routing table otherwise it will cause the destination host unreachable because even though the host exists but our device does not know how to reach the host.
If we will ping the Fast Ethernet 0/0 interface of router 4 from PC0 then we will get the unreachable error.
Download this Lab and try pinging the router 4 interface.
Fix – fix the issue by enabling routing dynamically or manually. Once router 3 will have information about the 192.168.3.0 network then router 3 will send the ping response.
Reason 3
Access list blocking the traffic
If traffic from any host is blocked by the access list then a destination host unreachable error will be received.
In the below example, traffic from host PC0 is blocked from reaching network 192.168.3.0 so the router is dropping the traffic received from this host, and ping packets are not able to reach the host PC1.
Download the lab and test the ping command and you will be able to see the packets blocked by the access list.
Fix – To fix the issue, either disable the access list or allow the traffic from PC0 on network 192.168.3.0
If we do not want to allow all traffic then only ICMP traffic can be blocked on the network. An extended access list can be used to block only ICMP traffic and allow the rest of the traffic from the host.
"Destination host unreachable" when pinging a pc from another network
I tried to build a simple network in Packet Tracer and I get "Destination host unreachable" when I try pinging a PC from another network. Pinging PCs from the same network works. When I use tracert to a PC from another network it stops at the current network default gateway. My guess it’s that it has something to do with the connections between the two routers, but I have no idea what exactly. I would be really grateful if someone could help me solve this problem. Thank you in advance. Here is the image of the network.
How to Fix Destination Host Unreachable Error?
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.
Either there is no device with the IP Address you typed or your computer has a corrupted ARP 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.
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.
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.
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Open the Command Prompt as Administrator
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Type cmd on the Windows Search
If the problem persists, you should run a traceroute to pinpoint the problem location.
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Open Command Prompt
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.
If the destination device is in your reach, make sure the device is on. Make sure the network connection is fine.
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.
About The Author:
Siju George is a Cisco and Microsoft certified Network Engineer. He has been working in the Network Engineering field since 2006.
Understanding Ping Responses,Destination unreachable,Request timed out,Reply
Here we are going to see ping responses network unreachable,request timed out,success with a simple topology by adding static route on each router step by step.
Step 1:Create a topology like this
Step 2:Routers only knows directly connected network,there is no static route added.Now, ping default gate way 10.0.0.1 from Host 10.0.0.10. we will get reply from 10.0.0.1.Because router knows 10.0.0.0 network.
PC>ping 10.0.0.1
Pinging 10.0.0.1 with 32 bytes of data:
Reply from 10.0.0.1: bytes=32 time=157ms TTL=255
Reply from 10.0.0.1: bytes=32 time=16ms TTL=255
Reply from 10.0.0.1: bytes=32 time=29ms TTL=255
Reply from 10.0.0.1: bytes=32 time=31ms TTL=255
Ping statistics for 10.0.0.1:
Packets: Sent = 4, Received = 4, Lost = 0 (0% loss),
Approximate round trip times in milli-seconds:
Minimum = 16ms, Maximum = 157ms, Average = 58ms
Step 3:Now ping host 40.0.0.10,we will get
PC>ping 40.0.0.10
Pinging 40.0.0.10 with 32 bytes of data:
Reply from 10.0.0.1: Destination host unreachable.
Reply from 10.0.0.1: Destination host unreachable.
Reply from 10.0.0.1: Destination host unreachable.
Reply from 10.0.0.1: Destination host unreachable.
Ping statistics for 40.0.0.10:
Packets: Sent = 4, Received = 0, Lost = 4 (100% loss),
Step 4:Add static route to Router R1 for the network 40.0.0.0
R1(config)#ip route 40.0.0.0 255.0.0.0 20.0.0.2
Now,Packets that came to Router R1 for the network 40.0.0.0 will be forwarded to 20.0.0.2
Check Routing table of R1 by giving command,
R1#show ip route
Codes: C — connected, S — static, I — IGRP, R — RIP, M — mobile, B — BGP
D — EIGRP, EX — EIGRP external, O — OSPF, IA — OSPF inter area
N1 — OSPF NSSA external type 1, N2 — OSPF NSSA external type 2
E1 — OSPF external type 1, E2 — OSPF external type 2, E — EGP
i — IS-IS, L1 — IS-IS level-1, L2 — IS-IS level-2, ia — IS-IS inter area
* — candidate default, U — per-user static route, o — ODR
P — periodic downloaded static route
Gateway of last resort is not set
C 10.0.0.0/8 is directly connected, FastEthernet0/0
C 20.0.0.0/8 is directly connected, Serial2/0
S 40.0.0.0/8 [1/0] via 20.0.0.2
We get reply from 20.0.0.1 because router R1 knows directly connected network.
Step 6:Now ping ip address 20.0.0.2
PC>ping 20.0.0.2
Pinging 20.0.0.2 with 32 bytes of data:
Request timed out.
Request timed out.
Request timed out.
Request timed out.
Ping statistics for 20.0.0.2:
Packets: Sent = 4, Received = 0, Lost = 4 (100% loss),
Router R2 doesn’t know about the network 10.0.0.0.So we can’t get reply from R2.Now add static route to router R2 for network 10.0.0.0 .Check routing table of R2
R2#show ip route
Codes: C — connected, S — static, I — IGRP, R — RIP, M — mobile, B — BGP
D — EIGRP, EX — EIGRP external, O — OSPF, IA — OSPF inter area
N1 — OSPF NSSA external type 1, N2 — OSPF NSSA external type 2
E1 — OSPF external type 1, E2 — OSPF external type 2, E — EGP
i — IS-IS, L1 — IS-IS level-1, L2 — IS-IS level-2, ia — IS-IS inter area
* — candidate default, U — per-user static route, o — ODR
P — periodic downloaded static route
Gateway of last resort is not set
C 20.0.0.0/8 is directly connected, Serial2/0
C 30.0.0.0/8 is directly connected, Serial3/