alias IP cannot communicate from VM

Hi everyone,
I'm stuck on trying to use an alias from a VM. Everything works from
its main ip address 10.0.0.53 but from an alias, in this case
172.16.20.1, I can't manage to make comms going out from it.

For example with "ping -I 172.16.20.1 <whatever-ip>" or openvpn binding
from it. There's no firewall active and there is no block from the
border firewall for that IP address. At this point I'm wondering if
that could work at all.

For the record the configuration of the VM is pretty much based on the
"Option 4" of the official OpenBSD guide at
https://www.openbsd.org/faq/faq16.html#VMMnet

any hing would be appreciated.
Thank you.



*** VSWITCH configuration
veb0: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST>
description: switch1-SWITCH01
index 7 llprio 3
groups: veb
em1 flags=3<LEARNING,DISCOVER>
port 2 ifpriority 0 ifcost 0
vport0 flags=3<LEARNING,DISCOVER>
port 8 ifpriority 0 ifcost 0
tap0 flags=3<LEARNING,DISCOVER>
port 11 ifpriority 0 ifcost 0
vport0: flags=8943<UP,BROADCAST,RUNNING,PROMISC,SIMPLEX,MULTICAST> mtu
1500
lladdr fe:e1:ba:d0:fa:31
description: INTERNAL
index 8 priority 0 llprio 3
groups: vport
inet 10.0.0.1 netmask 0xffffff00 broadcast 10.0.0.255

*** VM configuration
switch "SWITCH01" {
interface veb0
}
vm "VM-01" {
memory 800M
enable
disk /root/VM-01.qcow2
interfaces 1
interface { switch "SWITCH01" }
}

*** VM NIC output
vio0:
flags=808b43<UP,BROADCAST,RUNNING,PROMISC,ALLMULTI,SIMPLEX,MULTICAST,AU
TOCONF4> mtu 1500
lladdr fe:e1:bb:d1:0a:30
index 1 priority 0 llprio 3
groups: egress
media: Ethernet autoselect
status: active
inet 10.0.0.53 netmask 0xffffff00 broadcast 10.0.0.255
inet 172.16.20.1 netmask 0xffffffff