Identifying and Resolving Generic Router Problems
255
Checksum: 0x2bb5 [50-51]
Urgent Pointer: 0 [52-53]
TCP Options: [54]
Option Type: 2 Maximum Segment Size [55]
Length: 4
MSS: 1460 [56-58]
Option Type: 1 No Operation [59]
Option Type: 1 No Operation [60]
Option Type: 4 [61]
Length: 2
No More FTP Command or Reply Data
Frame Check Sequence: 0x00000000
Everything looks fine with this packet. Now, look at the ICMP message
received. Notice that the source IP address in the ICMP packet is from
172.16.60.1
. That is the gateway address for Host Z.
Flags: 0x00
Status: 0x00
Packet Length:74
Timestamp: 22:11:39.489000 04/18/1999
Ethernet Header
Destination: 00:a0:24:a5:06:57 [0-5]
Source: 00:10:7b:d9:28:81 [6-11]
Protocol Type:08-00 IP [12-13]
IP Header - Internet Protocol Datagram
Version: 4 [14 Mask 0xf0]
Header Length: 5 [14 Mask 0xf]
Precedence: 0 [15 Mask 0xe0]
Type of Service: %000 [15 Mask 0x1c]
Unused: %00 [15 Mask 0x3]
Total Length: 56 [16-17]
Identifier: 2815 [18-19]
Fragmentation Flags: %000 [20 Mask 0xe0]
Fragment Offset: 0 [20-22 Mask 0x1fffff]
Time To Live: 255
IP Type: 0x01 ICMP [23]
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