Re: Multi-Networking in Linux - Multiple Subnets
"Carlos E. R." <[email protected]> Sat, 1 Aug 2026 15:16:00 +0200
| Newsgroups | comp.os.linux.misc |
|---|---|
| Message-ID | <[email protected]> |
On 2026-08-01 14:49, Tauno Voipio wrote: > On 31.7.2026 14.51, Carlos E. R. wrote: >> On 2026-07-30 13:42, Marc Haber wrote: >>> "Carlos E. R." <[email protected]> wrote: >>>> eth0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 1500 >>>> inet 192.168.2.9 netmask 255.255.0.0 broadcast >>>> 192.168.255.255 >>> >>> Using the entire 192.168.0.0/16 range for a single home network is a >>> sure sign of a person not knowing too much about networking or an >>> incompetent ISP. >>> >>>> Works for me as above :-) >>> >>> Until the moment you'd want to connect to another network. >> >> >> >> LOL. I asked just now ChatGPT for the ranges, and it said: >> >> | Private range | CIDR notation | Number of >> addresses | Common use | >> | --------------------------------- | ---------------- | >> ------------------: | ----------------------------------------------- | >> | **10.0.0.0 – 10.255.255.255** | `10.0.0.0/8` | 16,777,216 | >> Large enterprise networks, cloud infrastructure | >> | **172.16.0.0 – 172.31.255.255** | `172.16.0.0/12` | 1,048,576 | >> Medium to large private networks | >> | **192.168.0.0 – 192.168.255.255** | `192.168.0.0/16` | 65,536 | Home >> routers and small office networks | >> >> Notice the last line... :-D >> > > Specifications for those address ranges are in RFC1918. Yes, ChatGPT is citing that document. The most commonly used private IPv4 address ranges are defined by Internet Engineering Task Force in RFC 1918: | CIDR | Address Range | Number of Addresses | | ---------------- | --------------------------------- | ------------------- | | `10.0.0.0/8` | `10.0.0.0` – `10.255.255.255` | 16,777,216 | | `172.16.0.0/12` | `172.16.0.0` – `172.31.255.255` | 1,048,576 | | `192.168.0.0/16` | `192.168.0.0` – `192.168.255.255` | 65,536 | > I looked at the document itself on https://datatracker.ietf.org/doc/html/rfc1918: 3. Private Address Space The Internet Assigned Numbers Authority (IANA) has reserved the following three blocks of the IP address space for private internets: 10.0.0.0 - 10.255.255.255 (10/8 prefix) 172.16.0.0 - 172.31.255.255 (172.16/12 prefix) 192.168.0.0 - 192.168.255.255 (192.168/16 prefix) We will refer to the first block as "24-bit block", the second as "20-bit block", and to the third as "16-bit" block. Note that (in pre-CIDR notation) the first block is nothing but a single class A network number, while the second block is a set of 16 contiguous class B network numbers, and third block is a set of 256 contiguous class C network numbers. So, stop saying that `192.168.0.0/16` is wrong, or that 172.16/12 is wrong. -- Cheers, Carlos E.R. ES🇪🇸, EU🇪🇺;