Problems with connectivity with VMs using virtio interfaces

Jul 6, 2023
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Hi,

I've got proxmox host running on a PC with single network interface. Inside, there are three linux VMs. Each one has network interface of virtio type. It worked just fine with Netgear Orbi Pro router. All hosts are located in one subnet, there are no VLANs. I switched to pfSense router installed on bare metal server. After the change only one VM has any connectivity. Others are able to communicate - trying to ping them either from the router itself or other physical hosts within the network gives host unreachable or host down error. I managed to bring some workaround changing interfaces to Intel E1000 and it works. What's interesting - when I switch back to virtio any VM it works again, but if I do it for the two of them - one stops to work, meaning that only one virtio interface can exist on single VM host. Has anyone seen such a problem?

Kal
 
Hi,

I've got proxmox host running on a PC with single network interface. Inside, there are three linux VMs. Each one has network interface of virtio type. It worked just fine with Netgear Orbi Pro router. All hosts are located in one subnet, there are no VLANs. I switched to pfSense router installed on bare metal server. After the change only one VM has any connectivity. Others are able to communicate - trying to ping them either from the router itself or other physical hosts within the network gives host unreachable or host down error. I managed to bring some workaround changing interfaces to Intel E1000 and it works. What's interesting - when I switch back to virtio any VM it works again, but if I do it for the two of them - one stops to work, meaning that only one virtio interface can exist on single VM host. Has anyone seen such a problem?

Kal
Hi,
please share the network configuration cat /etc/network/interfaces as well as the VM config for the VMs not having connectivity qm config <VMID>. You mention that the issue arouse after setting up a pfSense machine as router. Can you exclude that the issues are related to e.g. MAC filtering? You can check your routing table ip route and arp neighbors ip neigh, maybe that gives you a clue. Further, you can check via tcpdump -i vmbr0 the traffic going over the bridge to maybe spot issues when using the different NIC drivers.
 

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