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checking in- needs some refinement then done

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Brent S.
2025-02-09 23:07:25 -05:00
parent 64b669edc3
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README.adoc
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@@ -42,7 +42,17 @@ A tool to assist in design of segregate/segment/split/subnet networks.
** Note that for IPv6, some subnetting calculators erroneously report the last address for /64's (e.g. `x:ffff:ffff:ffff:ffff/64`) as usable. They are actually reserved in strictly RFC-compliant networks for EUI-64 reasons (per {rfc}2526[RFC 2526^]). For this reason, *if and only if* a prefix is a /64 *exactly*, `subnetter` will use `x:ffff:ffff:ffff:fffe` as the last host address.
** There are additional restrictions for /64 subnets, but they fall earlier in the range. These are *not explicitly excluded* in the usable host range, nor are they excluded from the total host count.
* Private networks ({rfc}1918[RFC 1918^]), ULA prefixes ({rfc}4193[RFC 4193^]), and documentation prefixes ({rfc}3849[RFC 3849^], {rfc}5737[RFC 5737^], {rfc}9637[RFC 9637^]) are treated as "normal" networks (in that it is allowed to subnet them).
* Various other reserved IPv4 and IPv6 addresses/networks will print warnings with their corresponding RFC(s) (unless `-R`/`--allow-reserved` is specified) if they are specified as/included in the initial prefix/network. ({rfc}6890[RFC 6890^] and its update via {rfc}8190[RFC 8190^] are useful summaries.)
* Various other reserved IPv4 and IPv6 addresses/networks will print warnings with their corresponding RFC(s) (unless `-R`/`--allow-reserved` is specified) if they are specified as/included in the initial prefix/network. ({rfc}6890[RFC 6890^] and its update via {rfc}8190[RFC 8190^] are useful summaries.) Note that for checking to function, an Internet connection is required as it pulls it directly from IANA live to ensure the data is accurate to standards. This may be cached locally if `-c`/`--cache-reservations` is specified, in which case a locally-cached copy will be used if present and populated then used if not.
** The cache directory may be specified by `-C`/`--cache-dir` (which can be specifically defaulted via the `SBNTR_RSVCACHE_DIR` environment variable). If it is not specified, the default (see below) will be used.
** This directory's default location determined by the following, and will be created if it doesn't exist:
*** For non-Windows systems (macOS, Linux, etc.)...
**** If https://specifications.freedesktop.org/basedir-spec/latest/#variables[the `XDG_CACHE_HOME` environment variable^] is present, it will be `${XDG_CACHE_HOME}/subnetter/`. (If XDG base dirs are enabled, this is usually `~/.cache/subnetter/` or, explicitly, `/home/<username>/.cache/subnetter/`)
**** If the `XDG_CACHE_HOME` environment variable is not present...
***** On macOS, an explicit fallback of `~/Library/Caches/subnetter/` will be used. (To my knowledge/understanding, this is the standard user cache directory and cannot be changed.) This usually evaluates to `/Users/<username>/Library/Caches/subnetter/`.
***** On all others, an explicit fallback of `~/.cache/subnetter` will be used.
****** On most non-macOS \*NIX-like systems , this is usually `/home/<username>/.cache/subetter/`, provided normal user homes. On http://p9f.org/[Plan9^] platforms (e.g. https://9p.io/plan9/index.html[Plan 9 4th Ed.^], https://9front.org/[9front^], http://9legacy.org/[9legacy^]), the `/env/home` environment variable (`$home`) will be used, the `./lib/` subdirectory under there (which typically/should already exist) will be appended to it, and that appended with `./cache/subnetter/` (this usually evaluates to `/usr/<username>/lib/cache/subnetter/`).
*** For Windows systems...
**** If https://learn.microsoft.com/en-us/windows/win32/shell/knownfolderid#constants[the `LOCALAPPDATA` environment variable^] is present, it will be `%LOCALAPPDATA%\Cache\subnetter\` (or `${env:LOCALAPPDATA}\Cache\subnetter\` in Powershell syntax). This usually evaluates to `C:\Users\<username>\AppData\Local\Cache\subnetter\`.
[id="ref"]
== References