tcpdump -i eth1 -np tcp port 1723
tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on eth1, link-type EN10MB (Ethernet), capture size 96 bytes
16:00:06.961083 IP 172.16.203.73.1060 > 192.168.1.1.1723: Flags [P.], seq 1352038095:1352038111, ack 1812086313, win 64135, length 16: pptp CTRL_MSGTYPE=ECHORQ ID(2264924160)
16:00:06.961232 IP 192.168.1.1.1723 > 172.16.203.73.1060: Flags [P.], seq 1:21, ack 16, win 7504, length 20: pptp CTRL_MSGTYPE=ECHORP ID(2264924160) RESULT_CODE(1) ERR_CODE(0)
16:00:06.966438 IP 192.168.1.1.1723 > 172.16.201.76.49244: Flags [P.], seq 3527416950:3527416966, ack 1577654691, win 16, length 16: pptp CTRL_MSGTYPE=ECHORQ ID(2030108672)
16:00:06.967458 IP 172.16.201.76.49244 > 192.168.1.1.1723: Flags [P.], seq 1:21, ack 16, win 16341, length 20: pptp CTRL_MSGTYPE=ECHORP ID(2030108672) RESULT_CODE(1) ERR_CODE(0)
16:00:06.967516 IP 192.168.1.1.1723 > 172.16.201.76.49244: Flags [.], ack 21, win 16, length 0
16:00:06.977993 IP 192.168.1.1.1723 > 172.16.202.62.2364: Flags [P.], seq 1103532844:1103532860, ack 1332799311, win 16, options [nop,nop,TS val 1259546576 ecr 389983182], length 16: pptp CTRL_MSGTYPE=ECHORQ ID(3323133952)
16:00:07.002038 IP 192.168.1.1.1723 > 172.16.192.107.1105: Flags [P.], seq 3057531371:3057531387, ack 2340098234, win 7504, length 16: pptp CTRL_MSGTYPE=ECHORQ ID(4177657856)
16:00:07.002823 IP 172.16.192.107.1105 > 192.168.1.1.1723: Flags [P.], seq 1:21, ack 16, win 64943, length 20: pptp CTRL_MSGTYPE=ECHORP ID(4177657856) RESULT_CODE(1) ERR_CODE(0)
16:00:07.002954 IP 192.168.1.1.1723 > 172.16.192.107.1105: Flags [.], ack 21, win 7504, length 0
16:00:07.016694 IP 172.16.202.62.2364 > 192.168.1.1.1723: Flags [P.], seq 1:21, ack 16, win 5840, options [nop,nop,TS val 389986187 ecr 1259546576], length 20: pptp CTRL_MSGTYPE=ECHORP ID(3323133952) RESULT_CODE(1) ERR_CODE(0)
16:00:07.016784 IP 192.168.1.1.1723 > 172.16.202.62.2364: Flags [.], ack 21, win 16, options [nop,nop,TS val 1259546586 ecr 389986187], length 0