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Host: Windows 10 64-bit

Guest: Ubuntu 16.04 32-bit

Networking: Wireless. Home network.

Host can ping Guest, and Guest can ping Host. Guest can also ping router. However, when I ping from my Guest to other hosts in LAN (when using bridged networking), the error returned is:

From <Guest's IP address> Destination Host Unreachable

I used Wireshark to troubleshoot and I saw the ARP to be like

Source: Host's MAC, Destination: Router, <Host's IP address is at Host's MAC> 
Source: Guest's MAC, Destination: Router, <Guest's IP address is at Guest's MAC>
Source: Host's MAC, Destination: Router, <Guest's IP address is at HOST's MAC>

So, there is a duplicate IP! My guest is unable to get the ARP reply from the other hosts in the LAN. I checked it with arp -a in the guest, and it is indeed incomplete for the other hosts in the LAN.

Do you guys have any idea?

ADDITIONAL INFO: The Guest is able to miraculously ping other hosts in the LAN in the afternoon, but then it could not.

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Host can ping Guest, and Guest can ping Host.

I don't know how you reach that conclusion. It sounds incorrect. If they both have the same IP, then what's happening is the Host can ping Host, and Guest and ping Guest. Each one is pinging its own IP address, not the other machine's IP address, even if you are using the other machine's (DNS) host name.

Whenever the guest tries to send a ping to anywhere, any replies are eaten up by the host because the host is using that IP address.

If you're using a bridged connection, then the guest should have a different IP address in the same subnet. If you're using automatic addressing (like DHCP/IPv4), then the guest should get such an address automatically. If you're statically assigning the IP address, then manually make the changes.

You may also want to double-check that the subnet mask and default gateway on the guest match those settings on the host. (With some setups, such settings should be different, but in the bridged setup that you describe, having them be the same is most likely the information that should be used.)

  • But the funny thing is that the Guest is able to ping the router and get the icmp replies. ifconfig also shows that the Guest has a different ip from host. – Kyoma Jan 19 at 8:57
  • You've updated the question after I provided the answer. The updated question has minor changes of quite important significance. Namely, you now say things have worked, and that a different IP address is sensibly being used. I feel like the original question has been answered, and if you want to know why the IP address changes, that's really a different question (that should be asked in a different question on SuperUser). Evolving questions on SuperUser are bad because the make clear-cut answers very challenging to provide (and/or read through). – TOOGAM Jan 19 at 9:06
  • Hi, I demurred. I have simply clarified my question. I agree with you that adding "things have worked in the afternoon" is significant, but I feel that you have not sufficiently answered my question. You assume that the IP address has changed, which is not the case. Both Host and Guest have different IP at the start. But I appreciate your answer. Thks. – Kyoma Jan 19 at 9:36
  • My assumption was that the IP address was different later, when things were working. If the IP address hasn't changed, then that's a problem. When there is an IP address conflict, different results can happen. We call this situation a "race condition". Sometimes one set of results will "win the race", while other times the race is lost and different results are gained. What must be done is to change the IP address. That will be one step to help solve things, and very well could be the only step you need to do. – TOOGAM Jan 19 at 9:41
  • I have edited my qns to include the fact that the correct mac-ip mapping for the Host and the incorrect one occurs in the same wireshark capture. Thus, the question becomes why does the host broadcast 2 different ARP. – Kyoma Jan 19 at 9:57

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