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So I recently installed a long rj45 cable to replace the powerline adapter I was using. I'm keeping the PLA in place as a failover but wanted to know if I will need to swap the connection by hand to make sure packets will take the fastest line to the router or if I can plug both lines to the router at the same time with no issues. Here's the network architecture:

            ~150M
        |---PLA----------|       
router--|                |SWITCH---other stuff
        |---RJ45---------|
            GIGABIT

Also, is there any significance to which ports are used on the switch (ie. priority)?

closed as off-topic by Ron Maupin Jun 17 at 22:43

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  • That depends completely on how you have configured your switch and your router. – Jörg W Mittag Jun 17 at 21:33
  • Unfortunately, questions about home networking and consumer-grade devices are explicitly off-topic here. You could try to ask this question on Super User. – Ron Maupin Jun 17 at 22:43
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if I can plug both lines to the router at the same time with no issues.

If the ports on the router are actual routed ports, you might be able to configure one as active and the other as "backup" interface, if the given vendor supports something like that. Still, chances are that this is not the case. Alternative: LACP between router and switch (see below). Might not be supported on that router.

If however, that router's LAN ports are actually ports of a built-in 4 port switch (and they are on most consumer-grade routers - which would make it off-topic for this site, anyway) and if neither switch nor router-integrated-switch support one variety of a spanning-tree protocol (which consumer-grade "unmanaged" hardware seldom do), you'll just build yourself a 300m packet loop racetrack. It will melt under self-generated/multiplied overload within something like 5 seconds after you hook up the first end device to the switch and it broadcasts its first ARP resolution request into the subnet.

Ethernet must have a star/tree/cascaded-star topology (at least logically), so parallel links, rings and loops must be detected and broken up. There's two main features for that:

  • Spanning Tree Protocols (802.1d, 802.1w, 802.1s, Cisco (Rapid-)PVST+ and probably some more) detect a loop and put one end of one link into blocking state.
  • Link Aggregation (802.3ad, LACP) merges two parallel links (of identical technical nature and speed) into one logical link.

Link-aggeration between a Powerline stretch and a Gigabit link would be asking for trouble, what with the large difference in speed and RTT you'll experience.

But the most fundamental problem of the intended setup might be this:

150m is 50% over max length for Cat5e (or better) twisted pair cabling with the usual 8P8C connectors (vulgo: RJ45). You'll be lucky if you can get a usable signal at the other end; with some trickery (like clocking down to 10Mbit/s and by fixing to full duplex mode from both ends), you might get away with it. But probably not at Gigabit speeds.

  • Thank you for your answer. The equipment is consumer grade - no management console or anything, just a dumb switch. I just wasn't sure how "dumb" it really is. For my purposes there's no issue leaving the auxiliary unplugged and swapping as needed. The PLA was a temporary measure. As for the cable I'm using, its a 150ft cat-6. The connection speeds are fine, though I probably wouldn't push it much farther without using switches as active repeaters of sorts. It's stupid, but hey, it works, so whatever. – Teddy Jun 17 at 23:59
  • Ah.. 150ft is a different ballpark than the "150m" I inferred from the ASCII sketch in your question. That explains why it works :-) – Marc 'netztier' Luethi Jun 18 at 6:38

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