Linux – How to connect a virtual NIC in one QEMU-KVM instance to a virtual NIC in another QEMU-KVM instance without a bridge

How did you set up the virtual machines in the new KVM server?

example: When you clone a virtual machine, KVM will generate new MAC ADDRESS for the interfaces... Since the MAC ADDRESS is not the same, the interfaces will have new names, because the interfaces files from the previous configuration are there, so, eth0 will not appear thus creating eth1 - At least this is how Red Hat like distros will behave..

Since you don't say what distro are you using, maybe checking the virtual machines MAC ADDRESS and change /etc/network/interfaces accordingly may help you..

The tap device's mac and the actual mac of the virtual NIC in the VM are different, this is why you see double the amount of MACs in the output.

You should only look at the VM's internal MACs, the ones you specify in the -net nic,vlan=0,macaddr=XX:XX... argument, the tap dev MACs aren't important.