we want to keep two connections of another segment at Target Site.
The Unity can not communication to Site① frome Site②, and vice versa.
yes if you are replicating from A to B than both systems need to be able to reach each other - both on mgmt network and replication mgmt/data ports
details on ports used are in the Unity security configuration guide
IMHO the setup in your picture should work IF you arent replication from source site 1 to source site 2
If it doesnt work open a service request so that it can be troubleshooted why
Site1 to replication target site.
Site2 to replication target site.
When the target site Unity has 2 replication interface(and connection), should the target site Unity see(and/or routing) all the network async replication ports?