What IPs need to be allowed through our Corp Firewall for SQL replication traffic outbound from our SQL Server CLuster?

I have a SQL Server 2008 R2 cluster with two nodes (active/passive). Here's the configuration :

                              Cluster name : MYCLUSTER .
                              Cluster IP : 123.123.0.10
                              Node 1 (active node) hostname : NODE1
                              Node 1 IP : 123.123.0.11
                              Node 2 (passive node) hostname : NODE2
                              Node 2 IP : 123.123.0.12
                              Instance Name: MYCLUSTER/MYINSTANCE
                              Instance IP: 123.123.0.13

                              I need to have my Network Folks open the Firewall (on Port 1433) to allow SQL Replication Traffic to a SQL Server outside of our Network. We opened the Firewall using the IP of the SQL Instance (123.123.0.13) but that did not do the trick. Can someone tell me what IPs have to be opened at the Firewall to allow the Replication Traffic?