Hello, I'm having a very interesting problem with a synchronous card and tcpdump. Everything works fine as far as communications (i.e. packets can flow through the link with no problems), but when I run tcpdump to look at the interface traffic, I only get garbage at tcpdump's output! With a ping traffic, for instance, this is what I get: # ifconfig hdlc1 hdlc1 Link encap:Point-to-Point Protocol inet addr:10.0.0.2 P-t-P:10.0.0.1 Mask:255.255.255.252 UP POINTOPOINT RUNNING NOARP MULTICAST MTU:1500 Metric:1 RX packets:7 errors:0 dropped:0 overruns:0 frame:0 TX packets:7 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:10 Interrupt:12 Memory:e0300000-e033ffff # tcpdump -i hdlc1 -n & [1] 1522 tcpdump: listening on hdlc1 # ping 10.0.0.1 14:48:43.139306 [|ip] 14:48:43.139852 [|ip] PING 10.0.0.1 (10.0.0.1): 56 data bytes 14:48:43.496968 64.1.96.160 > 10.0.0.2: (frag 17664:-27@672) [tos 0x3] 14:48:43.498130 30.1.136.72 > 10.0.0.1: (frag 17664:-27@672) [tos 0x3] [ttl 0] 14:48:43.498130 30.1.136.72 > 10.0.0.1: (frag 17664:-27@672) [tos 0x3] [ttl 0] 64 bytes from 10.0.0.1: icmp_seq=0 ttl=30 time=2.0 ms 14:48:44.489368 64.1.96.158 > 10.0.0.2: (frag 17664:-27@672) [tos 0x3] 14:48:44.490527 30.1.136.71 > 10.0.0.1: (frag 17664:-27@672) [tos 0x3] [ttl 0] 14:48:44.490527 30.1.136.71 > 10.0.0.1: (frag 17664:-27@672) [tos 0x3] [ttl 0] 64 bytes from 10.0.0.1: icmp_seq=1 ttl=30 time=2.0 ms 14:48:45.489366 64.1.96.155 > 10.0.0.2: (frag 17664:-27@672) [tos 0x3] 14:48:45.490535 30.1.136.70 > 10.0.0.1: (frag 17664:-27@672) [tos 0x3] [ttl 0] 14:48:45.490535 30.1.136.70 > 10.0.0.1: (frag 17664:-27@672) [tos 0x3] [ttl 0] 64 bytes from 10.0.0.1: icmp_seq=2 ttl=30 time=2.0 ms --- 10.0.0.1 ping statistics --- 3 packets transmitted, 3 packets received, 0% packet loss round-trip min/avg/max = 2.0/2.0/2.0 ms Just for comparison, what should show up is as follows (ping on the Ethernet interface): PING AA.BB.CC.EE (AA.BB.CC.EE): 56 data bytes 14:54:47.740150 AA.BB.CC.DD > AA.BB.CC.EE: icmp: echo request 14:54:47.741007 AA.BB.CC.EE > AA.BB.CC.DD: icmp: echo reply 64 bytes from AA.BB.CC.EE: icmp_seq=0 ttl=128 time=1.8 ms 14:54:48.739373 AA.BB.CC.DD > AA.BB.CC.EE: icmp: echo request 14:54:48.740193 AA.BB.CC.EE > AA.BB.CC.DD: icmp: echo reply 64 bytes from AA.BB.CC.EE: icmp_seq=1 ttl=128 time=1.3 ms 14:54:49.739369 AA.BB.CC.DD > AA.BB.CC.EE: icmp: echo request 14:54:49.740270 AA.BB.CC.EE > AA.BB.CC.DD: icmp: echo reply 64 bytes from AA.BB.CC.EE: icmp_seq=2 ttl=128 time=1.4 ms --- AA.BB.CC.EE ping statistics --- 3 packets transmitted, 3 packets received, 0% packet loss round-trip min/avg/max = 1.3/1.5/1.8 ms Does anyone here knows the possible cause(s) for this?? Does an interface have to meet some special requirements in order to be "listenable" by tcpdump?? :) TIA and Regards, Ivan - : send the line "unsubscribe linux-net" in the body of a message to majordomo@vger.rutgers.edu