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I am difficult to understand the following output generated from tcpdump:
tcpdump -i eth0 host 192.168.1.2 -n
09:33:07.862236 IP 192.168.1.2.137 > 192.168.1.255.137: NBT UDP PACKET(137): QUERY; REQUEST; BROADCAST
09:33:08.612389 IP 192.168.1.2.137 > 192.168.1.255.137: NBT UDP PACKET(137): QUERY; REQUEST; BROADCAST
09:33:09.363007 IP 192.168.1.2.137 > 192.168.1.255.137: NBT UDP PACKET(137): QUERY; REQUEST; BROADCAST
09:33:12.748227 IP 192.168.1.2.1034 > 22.214.171.124.53: 2758+ A? zonelabs.com. (30)
09:33:13.764453 IP 192.168.1.2.1034 > 126.96.36.199.53: 2758+ A? zonelabs.com. (30)
09:33:14.776041 IP 192.168.1.2.1034 > 188.8.131.52.53: 2758+ A? zonelabs.com. (30)
09:33:16.804434 IP 192.168.1.2.1034 > 184.108.40.206.53: 2758+ A? zonelabs.com. (30)
09:33:16.822431 IP 192.168.1.2.1034 > 220.127.116.11.53: 2758+ A? zonelabs.com. (30)
I see that the host 192.168.1.2 is sending packets from source port 1034 to netbios and DNS (18.104.22.168 is the DNS server of my provider) periodicaly. But what does it mean zonelabs.com. (30) - I have a zonealarm on this host (192.168.1.2) . Can anyone help me pls!
Source address churchward.erg.abdn.ac.uk
Source port 33635
Destination address gordon.erg.abdn.ac.uk
Destination port 32772
Indicates that the PUSH flag is set P
Sequence number (also start byte) 12765:
Contained data bytes from sqeuence number upto but not including 12925
Number of user data bytes in datagram (160)
Details of acknowledgements, Window size and Header flags ack 19829 win 24820 (DF)