Use snoop(1M) to check that packets are being transmitted. For example:
prompt# /usr/sbin/snoop -d ipdptp0 local -> remote RSHELL C port=1017 >0 'H ![ ? local -> remote RSHELL C port=1017 ,(!\nM/ local -> remote RSHELL C port=1017 Y@#K / ]0#Z ] 'Z local -> remote RSHELL C port=1017 .?;-)P3O89, " 2 H8" local -> remote RSHELL C port=1017 @ \#\ . . . |