Date: Wed, 25 Dec 2019 12:25:35 -0800
Subject: Re: [PLUG] Lan loops - follow on PoE injector
On Wed, Dec 25, 2019 at 9:33 AM Russell Senior <[email protected]>
wrote:

> Only one way to be sure! ;-)
>
>
Said the person on top of the building when contemplating if the fall would
kill him, while another person used factual data and applied higher level
abstract concepts such as math & physics to determine the most likely
outcome.  J/K Ha!

The OP is running OpenWrt on the router so this makes it far more
interesting, especially for Network Nerds like me, as OpenWrt is highly
configurable providing ample opportunities for experimentation.

According to this table from OpenWrt documentation, if the device type is
set to "bridge" then Spanning Tree Protocol can either be enabled or
disabled. (See screenshot "STP")

Even more interesting is that you might be able to even get a diagram of
the switch/router backplane that will show you how the ports are physically
& logically connected. Such as this diagram I found in the OpenWrt
documentation. (See attached screenshot "Diagram")

OpenWrt documentation refers to Asus WL-500G as a switch, however based on
the diagram the 4 LAN ports are physically bridged off Eth0 and the only
actual switching that happens appears to be between Eth0 (LAN) and Eth2
(WiFi).

I suspect this is a pretty common architecture for SOHO network gear.
Physically wired up, the LAN ports are a multi-port bridge. It's designed
to bridge 4 physical LANs into one logical LAN (VLAN 0) the default
management vlan.

OpenWrt would most certainly set the interface type to bridge and enable
STP thereby thwarting any layer 2 looping mischief.

But just disable STP in OpenWrt and have some fun!
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