port chain create fails for ports in different networks

Configuration

red hat open stack platform -11 ocata.

two networks
mgmt-network -- 172.16.0.0/24
insp-net 172.16.1.0/24

requirement : all service function vms will be connected to insp-network. other VMs(lets say vm1 and vm2) will be connected to mgmt-network.

created a port-pair and port-pair-group using ports in insp-network.
create a flow classifier using --logical-source-port of vm1 ( i.e all traffic that goes out of vm1 source port should go through sfc chaining).

Now when i create a port-chain using above mentioned PPG and FC in neutron server logs I see
"Cross-subnet not supported". port chaining is failed.

I wanted to steer traffic that is destined/originating to/from particular port in mgmt-network to go through service functions that are in different network i.e insp-network.
How I achieve this?.

p.s: I made it work if all the VMS and service functions are in the same network.

thanks
karim