Talk:Classless Inter-Domain Routing

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Internet Mid‑importance

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Confusion[edit]

How in the heck did I interpret 4 minutes as 3 months??!? - Lucky13pjn 19:48, Mar 14, 2005 (UTC)

External links[edit]

There are plenty of online network calculators, and the two ones in the external links are quite limited in functionalities. How about adding this one. --Olivier Debre 07:45, 14 April 2006 (UTC)[reply]

And how about adding this: http://vlsm-calc.net/. 80.250.189.67

Both of these are not really CIDR Calculators. A CIDR calculator needs to tell you if your CIDR is valid and then do the expansion and show the mask the range and stuff. These two are subneting calculators. The second does not really work. The first would be OK for the subneting article but someone can already see all these tables in the article . I suggest http://ipduh.com/ip/cidr a calculator actually used by people who use CIDR notation at work. Tenretnieht (talk)

All calculators have since been removed. ~Kvng (talk) 18:48, 20 April 2020 (UTC)[reply]

Refs, history for CIDR Notation?[edit]

I don't see any refs at all in the section on CIDR Notation. There is also no information about where this notation came from, or where it was first used. It is not used or described in RFC 1518 and RFC 1519, which defined CIDR.

I have heard that Phil Karn originally came up with the addr/netlength notation as a replacement for the cumbersome addr/dotteddecimalnetmask notation that required manually converting decimal to binary in your head to understand it, but I have no refs for that allegation either. RFC 1878 of December 1995 includes the "CIDR representation form" in a table of network masks, but does not explain the notation. I see that RFC 1918 in February 1996 uses the notation, but does not explain it, and calls previous approaches the "pre-CIDR notation". RFC 1924 from April 1996 describes "standard CIDR address/length notation" but again does not explain it or its history. Similarly RFC 2167 from June 1997 and RFC 2307 from March 1998. So it must have been invented in 1995 or early 1996, but when and by whom?

The first real *explanation* of CIDR notation in the RFC series is in RFC 2373 of July 1998 -- but that's for IPv6 addresses, not for IPv4 addresses, so not a great ref to use here. Help! Gnuish (talk) 13:22, 5 February 2019 (UTC)[reply]

Host Identifier: Contradictory Claim[edit]

Host identifier is defined as the least significant bits in an IP address following the network prefix bit (which are the most significant bits).

"IP addresses are described as consisting of two groups of bits in the address: the most significant bits are the network prefix, which identifies a whole network or subnet, and the least significant set forms the host identifier, which specifies a particular interface of a host on that network."

"An IP address is interpreted as composed of two parts: a network-identifying prefix followed by a host identifier within that network."

"An address was considered to be the combination of an 8, 16, or 24-bit network prefix along with a 24, 16, or 8-bit host identifier respectively."

etc.

Under "CIDR notation" the following is simply confusing, "The IP address is expressed according to the standards of IPv4 or IPv6. The address may denote a single, distinct interface address or the beginning address of an entire network. The aggregation of these bits is often called the host identifier."

This statement goes from talking about an IP address, which includes all the bits, to making the statement that "The aggregation of these bits is often call the host identifier." The way I read that is that all the bits in an IP address aggregated together are called the host identifier. This is obviously at odds with the definition of and other uses of "host identifier".

In fact, this contradictory sentence about the host identifier seems to be entirely unnecessary for the paragraph to make it's point. Host identifier is already defined, there'e little value in defining it again. Awisemanwillhear (talk) 19:02, 5 May 2020 (UTC)[reply]

@Kbrose: You modified the wording in question on July 2015 resulting in The aggregation of these bits is often called the host identifier. Perhaps that sentence should be removed? Johnuniq (talk) 00:22, 6 May 2020 (UTC)[reply]

Comparing the diff you presented with the current, indeed faulty text reveals that someone else must have jumbled the text later without reading everything for coherence. I reverted to previous prose with some copyediting. Kbrose (talk) 00:40, 6 May 2020 (UTC)[reply]

Thanks, I'm thinking about code at the moment and didn't really absorb what was going on here. Johnuniq (talk) 01:50, 6 May 2020 (UTC)[reply]

RFC links[edit]

RFC links seems broken? — Preceding unsigned comment added by XP 2600 (talk • contribs) 23:26, 21 July 2021 (UTC)[reply]

@XP 2600: Please quote some text from the article that we can search for to identify which link has a problem. This example seems to work: RFC 1518. By the way, click "new section" (might be "+" for you) at the top of the page to start a new topic. Johnuniq (talk) 02:38, 22 July 2021 (UTC)[reply]