Cisco Catalyst 2000 - Page 293

272 Cisco LAN Switching Configuration Handbook
Table B-1 shows the registered IP protocol numbers, along with the protocol keyword (or
acronym), the name of the protocol, and an RFC number (if applicable).
Table B-1 Registered IP Protocol Numbers, Keywords, Names, and Associated RFCs
Keyword Protocol References Number
HOPOPT 0
IPv6 Hop-by-Hop Option
RFC 1883
ICMP 1
Internet Control Message
RFC 792
IGMP 2
Internet Group Management
RFC 1112
GGP 3
Gateway-to-Gateway
RFC 823
IP 4
IP in IP (encapsulation)
RFC 2003
0123
Version Hdr len Service type Total length
Identification Flags Fragment offset
Time to live
Protocol Header checksum
Source IP address
Destination IP address
IP options (if needed) Padding
Data …
Figure B-1 IPv4 Header Format Showing the Protocol Field
Version
Traffic Class Flow Label
Payload Length
Hop Limit
"
"
Destination Address
"
"
Next Header
01
23
Source Address
"
"
Figure B-2 IPv6 Base Header Format Showing the Next Header Field