Connect OpenvSwitch to VM issue

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Joined: 2018/09/14 10:52:12

Connect OpenvSwitch to VM issue

Post by Arnaud » 2018/09/14 12:28:48


I would like to connect a CentOS 7 virtual machine to an Open vSwitch 2.5.0 (OVS) with SSH. The OVS is installed on a CentOS 7 physical server and the VM, which runs on the same server, is managed with VirtualBox. The interface in the OVS, called vnet7, is internal type, and has been added in VirtualBox as a Bridge.
I put the IP address in the OVS to enable it to communicate with the VM (the latter has the IP address
A schema of the configuration is attached.

The setup of OVS is as follows:
ovs-vsctl add-br ovs1
ovs-vsctl add-port ovs1 vnet7
ovs-vsctl set Interface vnet7 type=internal
ip link set vnet7 up
ip addr add dev ovs1
ip link set ovs1 up

In the server and the VM, ip routes are correct, there is no Iptables, Firewalld is disabled and SELinux is in permissive mode.
However, I do not manage to connect the VM to the OVS with SSH (or conversely to connect the server with OVS to the VM) whereas Nmap shows that port 22 is open.
In addition, I completed several tests:
• I can ping the OVS from the VM, and the VM from the physical server.
• UDP traffic generated with Iperf from the VM to the server is also working, but not conversely.
• If I connect another VM to the OVS (still installed on the same server), the 2 VMs are able to communicate with TCP.

A tcpdump in the server while launching a "ssh" from the VM shows that the server receives SYN flags but doesn’t reply with an ACK (see attached image "Tcpdump SSH server").
Same result when I launch a tcpdump in the VM and a "ssh" form the server (see attached image "Tcpdump SSH VM").

Do you have any idea about this kind of issue and the way to solve it?
Schema.png (5.8 KiB) Viewed 6224 times
Tcpdump SSH VM.png
Tcpdump SSH VM.png (71.8 KiB) Viewed 6224 times
Tcpdump SSH server.png
Tcpdump SSH server.png (46.23 KiB) Viewed 6224 times

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