FAQ-What Does First 8 bytes Mean in ICMP Debugging Information

Publication Date:  2015-07-02 Views:  269 Downloads:  0
Issue Description
What does First 8 bytes mean in ICMP debugging information?

*0.67607133 USG IP/8/debug_icmp:                                            
ICMP Send: host-unreachable(Type=3, Code=1), Src = 192.168.1.1, Dst = 192.168.1.
2; Original IP header: Pro = 17, Src = 192.168.1.2, Dst = 192.168.2.2, First 8 bytes = 05080045 001B0978
Solution
First 8 bytes indicate the first eight bytes of data bytes in an original IP packet. For example, in previous debugging information, the original packet is of the UDP type (protocol 17), and the first eight bytes in IP data is the UDP packet header. 0508 (in hexadecimal notation) indicates source port 1288 (in decimal notation); 0045 indicates destination port 69; 001B indicates that the UDP packet length is 27; 0978 indicates the checksum.

END