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Cisco LAN Switching Configuration Handbook, Second Edition by David Hucaby - CCIE No. 4594, David Jansen - CCIE No. 5952, Steve McQuerry - CCIE No. 6108

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Appendix BWell-known Protocol, Port, and Other Numbers

Refer to the following sections for explanations and listings of well-known numbers:

• B-1: IP Protocol Numbers

• B-2: ICMP Type and Code Numbers

• B-3: Well-known IP Port Numbers

• B-4: Well-Known IP Multicast Addresses

• B-5: Ethernet Type Codes

B-1: IP Protocol Numbers

A higher-layer protocol is identified with an 8-bit field within an IPv4 packet called Protocol. The IPv4 header format is shown in Figure B-1 with the Protocol field shaded. Figure B-2 shows the IPv6 header format where the protocol number is stored in the shaded Next Header field.

Figure B-1 IPv4 Header Format Showing the Protocol Field

Figure B-2 IPv6 Base Header Format Showing the Next Header Field

Well-known or ...

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