[ovirt-users] Strange Glitches with VM and Network (oVirt 4.4.4.7-1.el8)

Hi, I’m running oVirt 4.4.4.7-1.el8 and need to connect one of the VMs straight to the ISP link via Ethernet cable. oVirt already have 2 networks (ovirt mgmt local + DMZ). Created new network provider and assigned to it available physical interface of HP ProLiant, connected via cable to ISP switch with public IP. Options of this network: (VM Network = on, Port Isolation = off, NIC Type = VirtIO, the rest are defaults). VM is Debian 10. Link works but with strange artefacts. If VM left being idle for a while, it cant be connected or pinged from outside, until I initiate pings from VM itself. I have only 2 IPs from this ISP so I’m sure there are no IP address conflicts. Another port and public IP go to our VyOS router handling internal and DMZ zone. How to fix this problem ? Thanks in advance. Andrei