Path: csiph.com!fu-berlin.de!uni-berlin.de!individual.net!not-for-mail From: Robert Riches Newsgroups: comp.os.linux.misc Subject: Re: Multi-Networking in Linux - Multiple Subnets Date: 31 Jul 2026 04:06:43 GMT Organization: none-at-all Lines: 47 Message-ID: References: <114fdad$1trk7$1@news1.tnib.de> <114gf3s$24ndu$5@dont-email.me> Reply-To: spamtrap42@jacob21819.net Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Trace: individual.net WbliBnEq/7BVh03yhyBxeQC9ly8cdZMcIQ7SuapACJpEXezMGA Cancel-Lock: sha1:ggeR1tYebx3YulnTLqFDv8+Hl+Y= sha256:De4PI7NYpuBVolPX8ztAtDVL1v6rAS7x5DCiEDjKtGE= User-Agent: slrn/1.0.3 (Linux) Xref: csiph.com comp.os.linux.misc:89286 On 2026-07-31, c186282 wrote: > On 7/30/26 17:18, Lawrence D’Oliveiro wrote: >> On Thu, 30 Jul 2026 13:58:28 +0200, Carlos E. R. wrote: >> >>> The ISP configures the router so that it is mandatory to use >>> 192.168.1.*, and they take a good chunk of it for their own usage. I >>> have no recourse but using this non standard network. >> >> I remember seeing one setup -- I think in the house of a friend of a >> friend -- where there, not one, but *two* routers between the house >> LAN and the Internet. The outer one specified one private LAN, while >> the inner one put the house machines on an entirely different one. > > TWO routers ? UUUGGGH !!! Sounds like > a world of trouble ! Sounds can be deceiving. If the routers are arranged in series, you get what is sometimes referred to as double-NAT. You end up with three levels of network: - outer WAN with IP address provided by the ISP - middle ground, LAN to the outer router and WAN to the inner router - inner LAN A host in the middle ground can access the rest of the middle ground and the outer Internet. The middle ground can be used for less-trustworthy machines, like an employer's laptop or other Windows machines. It's somewhat like a DMZ. If printers must be accessed by the employer's laptop or other Windows machines, the printer can go in the middle ground. A host on the inner LAN can access the rest of the inner LAN, the middle ground, and the outer Internet. For an intruder to attack a host on the inner LAN, the intruder needs to break through both routers. Zoom and a few other services don't play well with double NAT, so Zoom and the like bad-mouth double NAT. If I ever really need to use Zoom, I'll use it from a Raspberry Pi in the middle ground. -- Robert Riches spamtrap42@jacob21819.net (Yes, that is one of my email addresses.)