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#1 2022-08-11 15:16:22

ewaller
Administrator
From: Pasadena, CA
Registered: 2009-07-13
Posts: 19,739

DNS propagation on an Internet Sharing Configuration

Question for those with more network savvy than I.

Regarding https://wiki.archlinux.org/title/Internet_sharing

I have a retired laptop I use as a media server and a 3D printer server.  It has a 480Mb WiFi link to my Asus router.
I also have a few devices attached to an unmanaged switch that is tied to my router through an Ethernet over Powerline extender.  The bandwidth of that is, well, suboptimum.  I want to get rid of that link and replace it with an Internet sharing configuration on the laptop to take advantage of its 10x bandwidth advantage and use the gigabit wired link to support the switch.

I have no concerns about setting up the wired network with a DHCP server, or with configuring IP Masquerading and IP forwarding. Been there, done that.

My question has to do with DNS.  My Asus router (with Merlin firmware) acts as my DHCP server on my LAN as it is currently configured.  It also acts as my DNS server and is cognizant of the host names on my domain,  (the domain name of my LAN is '.lan').  When I introduce a second DHCP server (on the laptop) for the new subnet, how does one go about propagating IP -> hostname.domain mappings back from the DHCP server on the laptop to the DNS server on the Asus router (or generally upstream in any local configuration)  ?

Last edited by ewaller (2022-08-11 15:16:54)


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#2 2022-08-11 17:17:50

Raynman
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Registered: 2011-10-22
Posts: 1,539

Re: DNS propagation on an Internet Sharing Configuration

Do you really want to go with that whole internet sharing setup? With double NAT and this second DHCP server? If you're only doing this for the bandwidth and not for some kind of network segregation, you should be looking at setting up a bridge.

If you do want a separate subnet, I imagine it would be easiest to use a different (sub)domain for that subnet and forward DNS queries for that domain to the laptop, but I don't have any experience with that.

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#3 2022-08-11 17:25:31

ewaller
Administrator
From: Pasadena, CA
Registered: 2009-07-13
Posts: 19,739

Re: DNS propagation on an Internet Sharing Configuration

Raynman wrote:

Do you really want to go with that whole internet sharing setup? With double NAT and this second DHCP server? If you're only doing this for the bandwidth and not for some kind of network segregation, you should be looking at setting up a bridge.

No, I would prefer a bridge.  Absolutely.

But, I was under the impression that one could only bridge WiFi devices if they can run in Promiscuous mode, and that that mode is generally unavailable in contemporary device firmware (IIRC because of regulatory domain issue).  If I am wrong, I would be delighted.

Edit: Of course, that moots the original issue as there is only one DHCP server and it is integrated with the DNS system in the router.

Last edited by ewaller (2022-08-11 17:37:26)


Nothing is too wonderful to be true, if it be consistent with the laws of nature -- Michael Faraday
Sometimes it is the people no one can imagine anything of who do the things no one can imagine. -- Alan Turing
---
How to Ask Questions the Smart Way

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#4 2022-08-11 17:50:54

Tarqi
Member
From: Ixtlan
Registered: 2012-11-27
Posts: 179
Website

Re: DNS propagation on an Internet Sharing Configuration

As you said, you (mostly) can not bridge a WiFi-Adapter in client mode, so the DHCP-Server on the Laptop needs to register the IPs in the DNS (edit: this might not be possible with your Asus router).

Edit 2: You might consider using routing and a DHCP-Relay instead of NAT, this could solve your problem (edit 3: for this, your Asus router must support a second DHCP-Scope).

The easiest option would be to get an (old?) cable-bound AP, put it into the switch and use it in client mode. No Laptop involved. There are several solutions, but it seems, the Asus router is the biggest problem here.

Last edited by Tarqi (2022-08-12 15:23:15)


Knowing others is wisdom, knowing yourself is enlightenment. ~Lao Tse

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#5 2022-09-25 19:34:50

Tarqi
Member
From: Ixtlan
Registered: 2012-11-27
Posts: 179
Website

Re: DNS propagation on an Internet Sharing Configuration

Edit: Removed due to no Interest/Answer from the OP.

Last edited by Tarqi (2022-10-23 20:50:51)


Knowing others is wisdom, knowing yourself is enlightenment. ~Lao Tse

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