No network connectivity between a KVM and a LXC host

[Matthieu Gaillet]

pve environment 5.4.6

Strange problem here. Two hosts configured with public IPs, one KVM and one LXC. They can't see each other.

They are on the same vmbr, same network, the network mask has been verified. Each machine has internet access and works perfectly. They can talk to the whole world except their neighbour.

The IPs are somewhat particular, they are part of a block of 4 "failover IP's" I bought at OVH. I double checked that the correct MAC adresses are used as per OVH's documentation.

I tested with two LXC machines using the same address block --> It works !

Therefore I suspect some proxmox config quirk that keeps a LXC and a KVM to talk each other. I tcpdumped trafic on the vmbr and didn't see anything else that traffic going to nowhere.

Any idea ?

Machine A :

#ifconfig
eth0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 1500
inet 151.x.x.2 netmask 255.255.255.252 broadcast 151.x.x.3

#routing
default via 5.x.x.254 dev eth0
5.x.x.254 dev eth0 scope link
151.x.x.0/30 dev eth0 proto kernel scope link src 151.x.x.2

Machine B :

# ifconfig
eth0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 1500
inet 151.x.x.1 netmask 255.255.255.252 broadcast 151.x.x.3

#routing
default via 5.x.x.254 dev eth0
5.x.x.254 dev eth0 scope link
151.x.x.0/30 dev eth0 proto kernel scope link src 151.x.x.1

 

[Matthieu Gaillet]

Update : someone confirmed that the FO ip's are normally able to talk each other between VMs.