For the scenario that is not working for you, i am able to reproduce it and what i see it's happening as both nics are from same network and as default route is of first nic it tries to go out via first nic. I am not sure if something can be handled on neutron/ovn side.
One way it worked for me was using ssh -b 192.168.10.21 100.7.50.237 or curl --interface eth1 100.7.50.237:22, also changing default route to be with eth1 instead of eth0 also worked.
Thanks ZhouHeng for checking.
For the scenario that is not working for you, i am able to reproduce it and what i see it's happening as both nics are from same network and as default route is of first nic it tries to go out via first nic. I am not sure if something can be handled on neutron/ovn side.
One way it worked for me was using ssh -b 192.168.10.21 100.7.50.237 or curl --interface eth1 100.7.50.237:22, also changing default route to be with eth1 instead of eth0 also worked.