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 assigned IP protocols are registered with the Internet Assigned Numbers Authority (IANA). The information ...

Get Cisco® Field Manual: Catalyst® Switch Configuration now with the O’Reilly learning platform.

O’Reilly members experience books, live events, courses curated by job role, and more from O’Reilly and nearly 200 top publishers.