Cannot ping between a Unix VM and a Windows VM in same subnet

Jones, Brian H 0

I am working on a LAB and I am just trying to establish ping my Unix VM which is running Ubuntu 20.04 and my Windows VM which is running Windows 11. While I am running EVE-NG on my Unix VM, both VMs have a public IP assigned and part of the same subnet that is assign to a single VM. Windows and Unix both have firewall disabled. If I reboot them a copy of times, it works about 20-30% of the time.

From a packet capture from the UNIX VM I see the following:

04:44:05.005882 IP lab-w11-pc.internal.cloudapp.net > eve-ng.internal.cloudapp.net: ICMP echo request, id 1, seq 164, length 40

04:44:05.010636 IP eve-ng.internal.cloudapp.net > 168.63.129.16: ICMP eve-ng.internal.cloudapp.net udp port 32995 unreachable, length 136

So I see the packet coming into the interface and the interface is set correctly as it gets DHCP and from my home PC, it works.

04:44:02.362624 IP 71-223-6-162.phnx.qwest.net > eve-ng.internal.cloudapp.net: ICMP echo request, id 2, seq 54225, length 40

04:44:02.362670 IP eve-ng.internal.cloudapp.net > 71-223-6-162.phnx.qwest.net: ICMP echo reply, id 2, seq 54225, length 40

So it is not working on the private side between the VMs.

KapilAnanth-MSFT 44,311 Reputation points Microsoft Employee

2023-10-31T06:44:44.9633333+00:00
@Jones, Brian H

Welcome to the Microsoft Q&A Platform. Thank you for reaching out & I hope you are doing well.

I understand that you are not able to ping between your Linux VM and Windows VM in the same subnet.

Can you please share the packet capture with IP address instead of hostname?

This is to confirm that the hostnames are properly resolving to the private IP of the VMs

Can you confirm the below

lab-w11-pc.internal.cloudapp.net - Hostname of windowsVM

eve-ng.internal.cloudapp.net - Hostname of linuxVM

May I ask what is "71-223-6-162.phnx.qwest.net"

Is that your OnPrem?

Also, you have shared the packet capture from LinuxVM side?

Can you share it from the windowsVM side?

Did the ICMP echo packet reach the windowsVM and windowsVM did not respond/dropped the packet?

Is the issue same for windowsVM ----> linuxVM as well?

Cheers, Kapil
Jones, Brian H 0 Reputation points

2023-10-31T11:57:06.9833333+00:00

Let me share some more info.

LAB-W11-PC is the hostname for the Windows VM, which has the private IP of 172.16.254.5 and its FDQN is lab-w11-pc.. EVE-NG-LAB3 (3rd iteration of EVE-NG) is the hostname of the Linux VM, which has a private IP of 172.16.254.5.

71.223.6.162 is my home machine to access the public side of both hosts. So when the issue happens, I can reach both machines, but they cannot see each other

I only did a packet capture on the Linux side but I will install Wireshark to do a capture on both sides and share the packet captures with IPs and share them shortly.
Jones, Brian H 0 Reputation points

2023-10-31T12:40:40.7566667+00:00

When I ping from Linux VM to Windows VM, I am not seeing the packets at all come into the Windows VM.

root@eve-ng:~# tcpdump -i pnet0 -n icmp

tcpdump: verbose output suppressed, use -v or -vv for full protocol decode

listening on pnet0, link-type EN10MB (Ethernet), capture size 262144 bytes

^C

0 packets captured

0 packets received by filter

0 packets dropped by kernel

When I ping from the Windows VM to the Linux VM, I see the packet leave the Windows VM and see it come into the Linux VM, but I never see the reply leave the Linux VM.

*WindowsVM

No. Time Source Destination Protocol Length Info

1 0.000000 172.16.254.5 172.16.254.4 ICMP 74 Echo (ping) request id=0x0001, seq=8/2048, ttl=128 (no response found!)

2 4.517000 172.16.254.5 172.16.254.4 ICMP 74 Echo (ping) request id=0x0001, seq=9/2304, ttl=128 (no response found!)

3 9.501774 172.16.254.5 172.16.254.4 ICMP 74 Echo (ping) request id=0x0001, seq=10/2560, ttl=128 (no response found!)

4 14.503422 172.16.254.5 172.16.254.4 ICMP 74 Echo (ping) request id=0x0001, seq=11/2816, ttl=128 (no response found!)

5 19.516388 172.16.254.5 172.16.254.4 ICMP 74 Echo (ping) request id=0x0001, seq=12/3072, ttl=128 (no response found!)

6 24.491425 172.16.254.5 172.16.254.4 ICMP 74 Echo (ping) request id=0x0001, seq=13/3328, ttl=128 (no response found!)

7 29.516416 172.16.254.5 172.16.254.4 ICMP 74 Echo (ping) request id=0x0001, seq=14/3584, ttl=128 (no response found!)

*Linux root@eve-ng:~# tcpdump -i pnet0 -n icmp

tcpdump: verbose output suppressed, use -v or -vv for full protocol decode

listening on pnet0, link-type EN10MB (Ethernet), capture size 262144 bytes

12:16:21.808067 IP 172.16.254.5 > 172.16.254.4: ICMP echo request, id 1, seq 8, length 40

12:16:26.325097 IP 172.16.254.5 > 172.16.254.4: ICMP echo request, id 1, seq 9, length 40

12:16:31.311153 IP 172.16.254.5 > 172.16.254.4: ICMP echo request, id 1, seq 10, length 40

12:16:36.311525 IP 172.16.254.5 > 172.16.254.4: ICMP echo request, id 1, seq 11, length 40

12:16:41.324640 IP 172.16.254.5 > 172.16.254.4: ICMP echo request, id 1, seq 12, length 40

12:16:46.299530 IP 172.16.254.5 > 172.16.254.4: ICMP echo request, id 1, seq 13, length 40

I power cycle the VM from the Portal again (stop/start) and it failed.

I went into the Serial Console and issue a "reboot" command as root and after the reboot it works. No configuration changes was made at all.

So eventually I get it to work, but I am trying to figure out why it takes a bit to get it to work correctly.
KapilAnanth-MSFT 44,311 Reputation points Microsoft Employee

2023-11-01T09:24:45.9233333+00:00
@Jones, Brian H

I take it that the

Private IP of Linux VM is 172.16.254.4 (you have mentioned it as 172.16.254.5)

And Private IP of Windows VM is 172.16.254.5

From the packet capture, (Windows VM to Linux VM)

We can clearly see the packets are being received by the Linux VM

This indicates that the platform routing is correct

However, the Linux VM is not even responding to the ICMP Ping requests.

This indicates there is some misconfiguration/issue in the OS of the Linux VM

In case the Linux VM has responded with a ICMP Ping reply and the Windows VM has not seen it, we can suspect there is a routing issue or packet drop at the platform.

Also, since you stated the issue is no longer reproducible once you had rebooted the system, further indicates this has something to do with the OS (OS level firewall/IP tables?)

Should the issue resurface again, I would suggest you to may file a support ticket, where a support engineer can have a specialized 1:1 screen share session to pinpoint the issue.

Should there be any follow-up questions or concerns, please let us know and we shall try to address them.

Thanks,

Kapil
KapilAnanth-MSFT 44,311 Reputation points Microsoft Employee

2023-11-02T08:42:45.2233333+00:00

@Jones, Brian H

I have summarized my comments and posted it as a new answer.

I would highly appreciate if you could Accept the answer and close this thread

Original posters help the community find answers faster by identifying the correct answer.

Thanks,

Kapil
KapilAnanth-MSFT 44,311 Reputation points Microsoft Employee

2023-11-03T06:12:42.3366667+00:00

@Jones, Brian H

Reaching out to check if there are any questions on this.

Please let us know if we can be of any further assistance here.

Thanks,

Kapil

Please Accept an answer if correct.

Original posters help the community find answers faster by identifying the correct answer.

1 answer

KapilAnanth-MSFT 44,311 Reputation points Microsoft Employee

2023-11-02T08:44:51.4+00:00
@Jones, Brian H

Welcome to the Microsoft Q&A Platform. Thank you for reaching out & I hope you are doing well.

I understand that you are not able to ping between your Linux VM and Windows VM in the same subnet.

I take it that the

Private IP of Linux VM is 172.16.254.4

And Private IP of Windows VM is 172.16.254.5

From the packet capture, (Windows VM to Linux VM)

We can see the packets are being received by the Linux VM

This indicates that the platform routing is correct

However, the Linux VM is not even responding to the ICMP Ping requests.

This indicates there is some misconfiguration/issue in the OS of the Linux VM

In case the Linux VM has responded with a ICMP Ping reply and the Windows VM has not seen it, we can suspect there is a routing issue or packet drop at the platform.

Also, since you stated the issue is no longer reproducible once you had rebooted the system, further indicates this has something to do with the OS (OS level firewall/IP tables)

Should the issue resurface again, I would suggest you to may file a support ticket, where a support engineer can have a specialized 1:1 screen share session to pinpoint the issue.

Kindly let us know if this helps or you need further assistance on this issue.

Thanks,

Kapil

Please don’t forget to close the thread by clicking "Accept the answer" wherever the information provided helps you, as this can be beneficial to other community members.
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