I am running a server with Debian 8.3, uname output
Linux x 3.16.0-4-amd64 #1 SMP Debian 3.16.7-ckt20-1+deb8u3 (2016-01-17) x86_64 GNU/Linux
I am using KVM to run a virtual machine with CentOS 7.2.1511 inside it, there are two network interfaces on the host and two network interfaces on the guest using bridges and virt-io.
One of the network interfaces is used for receiving multicasts (around 300mbps, received on the host's eth1 device) and it has packet loss, with the dropped packets visible on the host on "vnet1" interface. I increased the txqueuelen of the interface and the drop counter no longer increases, but packets are still lost.
I tried using virt-io, e1000 and rtl8139 drivers and macvtap (passtrough mode), it all results in more or less packet loss which is a big problem for multicasts. The server cpu usage is low.
How do I make the virtual network behave correctly.