in addition - we can see traffic between members over eth1-Sync:
[Expert@ADE-CHKP-R82EA-SMO-s01-02:0]# tcpdump -nni eth1-Sync host 192.0.2.1
tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on eth1-Sync, link-type EN10MB (Ethernet), capture size 262144 bytes
15:59:27.365392 IP 192.0.2.1.1135 > 192.0.2.255.1135: UDP, length 807
15:59:27.392815 IP 192.0.2.2.36379 > 192.0.2.1.6380: Flags [.], seq 614975352:614976800, ack 1404429924, win 29, options [nop,nop,TS val 3941735243 ecr 2301092449], length 1448
15:59:27.392834 IP 192.0.2.2.36379 > 192.0.2.1.6380: Flags [.], seq 1448:2896, ack 1, win 29, options [nop,nop,TS val 3941735243 ecr 2301092449], length 1448
15:59:27.392837 IP 192.0.2.2.36379 > 192.0.2.1.6380: Flags [.], seq 2896:4344, ack 1, win 29, options [nop,nop,TS val 3941735243 ecr 2301092449], length 1448
15:59:27.393060 IP 192.0.2.2.36379 > 192.0.2.1.6380: Flags [P.], seq 4344:4654, ack 1, win 29, options [nop,nop,TS val 3941735244 ecr 2301092449], length 310
15:59:27.393335 IP 192.0.2.1.6380 > 192.0.2.2.36379: Flags [.], ack 4654, win 179, options [nop,nop,TS val 2301101025 ecr 3941735243], length 0
15:59:27.393399 IP 192.0.2.1.6380 > 192.0.2.2.36379: Flags [P.], seq 1:23, ack 4654, win 179, options [nop,nop,TS val 2301101025 ecr 3941735243], length 22
15:59:27.393451 IP 192.0.2.2.36379 > 192.0.2.1.6380: Flags [.], ack 23, win 29, options [nop,nop,TS val 3941735244 ecr 2301101025], length 0
15:59:28.097169 IP 192.0.2.1.34456 > 192.0.2.2.6380: Flags [.], seq 1155514033:1155515481, ack 3414838712, win 29, options [nop,nop,TS val 2301101729 ecr 3941727387], length 1448
15:59:28.097241 IP 192.0.2.1.34456 > 192.0.2.2.6380: Flags [.], seq 1448:2896, ack 1, win 29, options [nop,nop,TS val 2301101729 ecr 3941727387], length 1448
15:59:28.097247 IP 192.0.2.1.34456 > 192.0.2.2.6380: Flags [.], seq 2896:4344, ack 1, win 29, options [nop,nop,TS val 2301101729 ecr 3941727387], length 1448
15:59:28.097252 IP 192.0.2.1.34456 > 192.0.2.2.6380: Flags [P.], seq 4344:4663, ack 1, win 29, options [nop,nop,TS val 2301101729 ecr 3941727387], length 319
15:59:28.097601 IP 192.0.2.2.6380 > 192.0.2.1.34456: Flags [.], ack 4663, win 179, options [nop,nop,TS val 3941735948 ecr 2301101729], length 0
15:59:28.097811 IP 192.0.2.2.6380 > 192.0.2.1.34456: Flags [P.], seq 1:23, ack 4663, win 179, options [nop,nop,TS val 3941735949 ecr 2301101729], length 22
15:59:28.097931 IP 192.0.2.1.34456 > 192.0.2.2.6380: Flags [.], ack 23, win 29, options [nop,nop,TS val 2301101730 ecr 3941735949], length 0
^C