output: don't use /etc/protocols
Using /etc/protocols leads to subtle differences in output. E.g. in ICMPv6 we have
IPv6-ICMP on Ubuntu, but
IPV6-ICMP on FreeBSD 12. Alpine Linux with musl doesn't define SCTP and so on.
Updated by Jeff Lucovsky 8 months ago
Suggest using the names/values in the authoritative source: https://www.iana.org/assignments/protocol-numbers/protocol-numbers.xhtml#protocol-numbers-1
Or, did you have something else in mind -- start with ubuntu?