Hi
This is the short answer (the complete answer will be added to the relevant ClusterXL Admin Guides and relevant SK articles)
(1)
In R81 and higher versions (due to merge of the Scalable Platform code):
To perform a Full Sync with a peer cluster member, the CXLD daemon on a cluster member connects to the TCP port 263 on the peer cluster member
If this connection fails, then the cluster member falls back to the previous mechanism - the FWD daemon connects to the TCP port 256 on the peer cluster member
(2)
In R80.40 and lower versions:
To perform a Full Sync with a peer cluster member, the FWD daemon on a cluster member connects to the TCP port 256 on the peer cluster member