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Chapter 5
Applying Cisco's Diagnostic Tools
Header Checksum: 0xe021 [24-25]
Source IP Address: 172.16.60.1 [26-29]
Dest. IP Address: 172.16.60.130 [30-33]
No Internet Datagram Options
ICMP - Internet Control Messages Protocol [34]
ICMP Type: 3 Destination Unreachable [35]
Code: 1 Host Unreachable
Checksum: 0x6439 [36-37]
Unused (must be zero):0x00000000 [38-41]
Header of packet that caused error follows.
IP Header - Internet Protocol Datagram
Version: 4 [42 Mask 0xf0]
Header Length: 5 [42 Mask 0xf]
Precedence: 0 [43 Mask 0xe0]
Type of Service: %000 [43 Mask 0x1c]
Unused: %00 [43 Mask 0x3]
Total Length: 48 [44-45]
Identifier: 17152 [46-47]
Fragmentation Flags: %010 Do Not Fragment [48 Mask
0xe0]
Fragment Offset: 0 [48-50 Mask 0x1fffff]
Time To Live: 127
IP Type: 0x06 TCP [51]
Header Checksum: 0x1a23 [52-53]
Source IP Address: 172.16.60.130 [54-57]
Dest. IP Address: 172.16.10.2 [58-61]
No Internet Datagram Options
TCP - Transport Control Protocol
Source Port: 1038 [62-63]
Destination Port: 21 FTP Control - File Transfer
Protocol [64-65]
Sequence Number: 6198340 [66-69]
Ack Number: 0
The key information is provided under the ICMP header section. Notice
the ICMP type of 3, which is equivalent to an unreachable destination--the
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