Hello peeps :))
The standard IP header length is 20 bytes. The "Routing TCP/IP Volume 1" book indicates on page 33 that with options set within the IP header, the sizes can be variable from 20 bytes "upto a maximum size of 24 bytes."
So I wanted to see an IP packet with options in the header to verify this fact, so I did a record route ping. Here is what I found in the packet. I assume that there is an explication to this and it has something to do with EIP (extended IP formats which I know nothing about)
Can anyone help?
Internet Protocol, Src Addr: 10.1.1.1 (10.1.1.1), Dst Addr: 10.1.1.253 (10.1.1.253)
Version: 4
Header length: 60 bytes
Full frame below:-
Frame 245 (114 on wire, 114 captured)
Arrival Time: Apr 25, 2003 19:56:58.631923000
Time delta from previous packet: 0.000092000 seconds
Time relative to first packet: 50.166327000 seconds
Frame Number: 245
Packet Length: 114 bytes
Capture Length: 114 bytes
Ethernet II
Destination: 00:10:f6:a8:18:00 (Cisco_a8:18:00)
Source: 00:d0:ba:e2:21:41 (Cisco_e2:21:41)
Type: IP (0x0800)
Internet Protocol, Src Addr: 10.1.1.1 (10.1.1.1), Dst Addr: 10.1.1.253 (10.1.1.253)
Version: 4
Header length: 60 bytes
Differentiated Services Field: 0x00 (DSCP 0x00: Default; ECN: 0x00)
0000 00.. = Differentiated Services Codepoint: Default (0x00)
.... ..0. = ECN-Capable Transport (ECT): 0
.... ...0 = ECN-CE: 0
Total Length: 100
Identification: 0x0004
Flags: 0x00
.0.. = Don't fragment: Not set
..0. = More fragments: Not set
Fragment offset: 0
Time to live: 255
Protocol: ICMP (0x01)
Header checksum: 0x8963 (correct)
Source: 10.1.1.1 (10.1.1.1)
Destination: 10.1.1.253 (10.1.1.253)
Options: (40 bytes)
Record route (39 bytes)
Pointer: 8
10.1.1.1
- <- (current)
-
-
-
-
-
-
-
EOL
Internet Control Message Protocol
Type: 8 (Echo (ping) request)
Code: 0
Checksum: 0x4c00 (correct)
Identifier: 0x1b93
Sequence number: 16:cf
Data (32 bytes)
0000 00 00 00 00 00 11 6b e8 ab cd ab cd ab cd ab cd ......k.........
0010 ab cd ab cd ab cd ab cd ab cd ab cd ab cd ab cd ................
