Centos 7 couldn't communicate to Windows servers in Layer 2

Issues related to configuring your network
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Arniold
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Joined: 2022/06/16 13:46:41

Centos 7 couldn't communicate to Windows servers in Layer 2

Post by Arniold » 2022/06/16 14:10:45

Hello everybody,

I've build a Lab to test some applications, the LAB include next:

1 ESX host
3 Portgroups (Networks) in Layer 2 only
Network segments:
192.168.201.0/24
192.168.202.0/24
192.168.203.0/24

3 Centos7 VMs which have 3 vNic each VM
centos-01
Nic1:192.168.201.1/24
Nic2:192.168.202.1/24
Nic3:192.168.203.1/24
centos-02
Nic1:192.168.201.2/24
Nic2:192.168.202.2/24
Nic3:192.168.203.2/24
centos-03
Nic1:192.168.201.3/24
Nic2:192.168.202.3/24
Nic3:192.168.203.3/24
2 Windows server 2019 VM which have 3 vNic in each vm
Win-01
Nic1:192.168.201.10/24
Nic2:192.168.202.10/24
Nic3:192.168.203.10/24
Win-02
Nic1:192.168.201.20/24
Nic2:192.168.202.20/24
Nic3:192.168.203.20/24


All VMs located on same ESX host. the portgroup assignment to each VM compatible to IP configuration on same NIC so it's configured well.

the issue is;
I'm successfully pinging between all centos VM to each other
I'm successfully pinging between 2 Windows VMs to themselves to each other

i cannot pinging between Centos7 VM to Windows VM and opposite.
there is no firewall between them cause it's same "LAN", and firewall on windows and centos7 was turned off.

centos7 version is 7.9.2009


Does anyone encounter with this issue or know a solution for it?

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TrevorH
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Re: Centos 7 couldn't communicate to Windows servers in Layer 2

Post by TrevorH » 2022/06/16 16:49:32

Are all VMs hosted on the same server? What do you get from ip route get 192.168.whatever on a CentOS VM?
CentOS 8 died a premature death at the end of 2021 - migrate to Rocky/Alma/OEL/Springdale ASAP.
Info for USB installs on http://wiki.centos.org/HowTos/InstallFromUSBkey
CentOS 5 and 6 are dead, do not use them.
Use the FAQ Luke

Arniold
Posts: 4
Joined: 2022/06/16 13:46:41

Re: Centos 7 couldn't communicate to Windows servers in Layer 2

Post by Arniold » 2022/06/17 07:28:04

All VMs hosted on same server
see the screenshot below:
ip route results
ip route results
Capture.PNG (27.13 KiB) Viewed 358 times

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TrevorH
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Re: Centos 7 couldn't communicate to Windows servers in Layer 2

Post by TrevorH » 2022/06/17 08:31:55

Since I don't know your network card names or anything much else about your system, you need to answer the question about whether ens161 is the correct interface for the traffic in question.
CentOS 8 died a premature death at the end of 2021 - migrate to Rocky/Alma/OEL/Springdale ASAP.
Info for USB installs on http://wiki.centos.org/HowTos/InstallFromUSBkey
CentOS 5 and 6 are dead, do not use them.
Use the FAQ Luke

Arniold
Posts: 4
Joined: 2022/06/16 13:46:41

Re: Centos 7 couldn't communicate to Windows servers in Layer 2

Post by Arniold » 2022/06/17 09:25:42

yes the ens161 is correct interface for a traffic.


very weird issue this interface successfully communicate with other Centos VMs, but cannot communicate with Windows VMs and opposite and the portgroup(network card) is the same and they're all on the same server

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TrevorH
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Joined: 2009/09/24 10:40:56
Location: Brighton, UK

Re: Centos 7 couldn't communicate to Windows servers in Layer 2

Post by TrevorH » 2022/06/17 09:42:29

I'd fire up wireshark and trace the traffic. It's available on Windows too so set it up on both sides to catch specific traffic like 'icmp and host 192.168.x.x -i ens161 -n -nn -l' then ping from the other side and see if the traffic appears. On CentOS I know that wireshark 'sees' traffic before it hits the firewall so you can see packets arrive even if they are subsequently dropped by the firewall. I presume it's the same on Windows but do not know if it is or not.
CentOS 8 died a premature death at the end of 2021 - migrate to Rocky/Alma/OEL/Springdale ASAP.
Info for USB installs on http://wiki.centos.org/HowTos/InstallFromUSBkey
CentOS 5 and 6 are dead, do not use them.
Use the FAQ Luke

Arniold
Posts: 4
Joined: 2022/06/16 13:46:41

Re: Centos 7 couldn't communicate to Windows servers in Layer 2

Post by Arniold » 2022/06/17 13:27:53

I'll check with sniffing but it seems like something wrong with centos configuration (Default Configuration) cause it's clean image from Centos website.
maybe after VM installation there is some configuration that should be done on basic level

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TrevorH
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Posts: 32025
Joined: 2009/09/24 10:40:56
Location: Brighton, UK

Re: Centos 7 couldn't communicate to Windows servers in Layer 2

Post by TrevorH » 2022/06/17 13:54:23

No idea. The purpose of packet sniffing is to gather data so you can find out what is going on. At present, all you have is guesswork and that doesn't usually work.
CentOS 8 died a premature death at the end of 2021 - migrate to Rocky/Alma/OEL/Springdale ASAP.
Info for USB installs on http://wiki.centos.org/HowTos/InstallFromUSBkey
CentOS 5 and 6 are dead, do not use them.
Use the FAQ Luke

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