IP Header Max Length

[Ciscomania]

The norm IP Header is 20 byte size (5*32=160 bit = 20 bytes)
The max size is 60 byte(15*32=480 bit = 60 bytes)
In which case we can have IP Header more than 20 bytes? for example maximum 60 bytes IP HEADER?

Thank you in advance

[David_Che · Accepted solution]

Yes, IP header length occupied 4 bits in IP header, that means its maximum value is 1111=15. So the maximum is 15 *4 bytes =60 bytes.The normal IP header is 20 bytes, the left 40 bytes are reserved to IP option and padding, including loose, timestamp and etc. For more IP options, you can refer the following link.

http://www.iana.org/assignments/ip-parameters/ip-parameters.xhtml

HTH,

David