Adding router interfaces after VM's spawned doesn't work

Reproducible scenario:

• One host
• 2 networks. No router interface on these networks yet
• Spawn two VMs- VM1 with net1, VM2 with net2
• Add default gw in the VM (route add default gw <IP>)
• Add router interfaces in each network

Ping between VM’s doesn’t work.

If I create the router interfaces prior to spawning the VM’s it works fine.

Pipeline:
0->17->40->41->17->19->80->17->50->51->52->group->group->55->
cookie=0x880fce3, duration=3827.246s, table=55, n_packets=3802, n_bytes=3596350, priority=10,tun_id=0xfce3,metadata=0xfce30000000000/0x1fffff0000000000 actions=dr
op