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How to connect three machines (Mini, 10.11; laptop, 10.12; iMac, 10.13) on two local networks, one wired and one WiFi, where local traffic is over wired connections and (external) Internet traffic is over WiFi? For context, assume the WiFi router is in another part of the building, wired connections to it are not an option and it is not under my control. The primary motivation is to do all file sharing among the three machines (TimeMachine backups and other networked file sharing) on higher bandwidth connections. What are the essential details of this configuration?

The Mini has 1 Ethernet port and 1 Thunderbolt port. The iMac has 1 Ethernet and 2 Thunderbolt ports. The laptop has only Thunderbolt ports (but one could always get a dongle). (All have Wifi.) The interface priority on all machines is set to: Thunderbolt, then (if on the machine) Ethernet, and then WiFi. Is this interface priority scheme helpful or counterproductive?

IP addresses for Thunderbolt and Ethernet are manually set to a subnet different than that of the the WiFi router (10.0.10.x, masked with 255.255.255.0, for wired local connections and 10.0.0.x for WiFi).

Option 1. Thunderbolt daisy chain. Can I daisy chain the local wired network and expect the endpoints to communicate via Thunderbolt cables: Mini (10.0.10.1) <-> iMac (10.0.10.2) and iMac (10.0.10.2) <-> laptop (10.0.10.3)? If yes, do I need to do anything specific to make this happen? For instance, on the laptop (and Mini) would I need to add something in the routing table (or other file) that says something like, "for all packets going to 10.0.10.x, use interface bridge0"?

Option 2. Direct connections for each pairing of machines. The machines could be connected in a triangular configuration: Mini (10.0.10.1) <-> iMac (10.0.10.2), iMac (10.0.10.2) <-> laptop (10.0.10.3), and Mini (10.0.10.1) <-> laptop (10.0.10.3). Given the available ports (see above), the model would then be to connect the Mini and iMac via Ethernet and connect the laptop to each other machine via Thunderbolt. Under this scenario, would the Ethernet and Thunderbolt interfaces need to be on separate subnets, i.e., : Mini (10.0.11.1) <-> iMac (10.0.11.2), iMac (10.0.10.2) <-> laptop (10.0.10.3), and Mini (10.0.10.1) <-> laptop (10.0.10.3)?

  • confusing question, but it must be me. What is the function in connecting 3 Mac's over cable ? File transfer, Target Disk mode ? other ? – Ruskes Aug 27 '18 at 16:13
  • It would help to know which computers have Thunderbolt, which Ethernet and which a Wi-Fi card. – jaume Aug 27 '18 at 16:31
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    I'm sorry, but I don't understand what you're trying to achieve by this. – AlanGBaker Aug 27 '18 at 17:35
  • The post was edited to clarify what I am hoping to do and why. Please let me know if things are still unclear. I am a bit of a networking newbie so, I may be grasping in the wrong direction or without proper insight. – jbjo Aug 27 '18 at 18:07
  • I think the simplest way is to get a router. Wire all your devices. Local traffic should flow on the wired network. Get a router that allows you to configure it in a bridge configuration. – historystamp Jan 26 at 21:38
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Note: Answer not complete....

"Local" Data

Home network with wired and WiFi, force local data over wired

There's a bit of a rhetorical question here - what's local data? The answers will vary depending on how you see this whole thing configured however, we have to step away from that and look at from the perspective of the network.

In other words, "local data" is data that resides (is local to) that particular network. Let's look at your two networks: 10.0.10.0 and 10.0.11.0. We'll call them 10.0 and 11.0, respectively for the sake of brevity.

Traffic sent on 10.0 to a particular node, say 10.25 is local to that network. Likewise, traffic sent on 11.0 on the same network is considered local to it. This is all traffic - web, ssh, ftp, smb, etc.

Multiple Networks, Multiple Adapters

Can a node (computer) have two or more network adapters to connect to multiple networks? Sure!

You don't even need multiple adapters if your equipment makes use of 802.1Q VLAN (Virtual LAN) specification (we'll save that for another day). However, you can attach multiple network interfaces to a single node to access more than one network.

Dual Network

In this scenario, we have a single node with two network adapters connected to two different networks, 10.0 and 11.0.

  • To clarify, the sense of "local" intended (in the post title) is the commonplace meaning, not a technical usage: Data traffic that is strictly among the three machines described in the scenario (whatever the road taken). As for enumeration of local networks, granted, there would be two (10.0.0.x and 10.0.10.x) in Option 1 or three (10.0.0.x, 10.0.10.x, and 10.0.11.x) in Option 2. The goal is to only use 10.0.0.x (i.e., WiFi) for low volume "local" traffic and outbound "Internet" traffic. – jbjo Aug 29 '18 at 2:13

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