Just to add, I've currently set things up as follows:
Modem > time capsule (which creates a wireless network) > powerline adapter 1 > powerline adapter 2 > airport express (which creates a wireless network)
I'm connecting the iMac via wifi to the time capsule, but would much rather connect via ethernet. Is there any way to connect to the time capsule without messing things up, or would using another powerline adapter be the only way?
modem > time capsule (which creates a wireless network) > powerline adapter 1 * > powerline adapter 2 > airport express
* But as well as connecting an ethernet cable to powerline adapter 1, also connect one from TC to my iMac.
When I tried connecting an ethernet cable to the TC in my original setup, the iMac lost connection to the internet. I've managed to get the following setup to work:
What you are attempting should work fine. The TC should be able to manage multiple ethernet connections as well as the wireless.
Investigate what is happening when you plug ethernet into the TC from the imac.
Please try it.. turn off wireless in the imac to ensure ethernet is the only connection.
But I would recommend you shut off the whole network at that point. Restart everything in order.. modem .. TC.. EOPs.. Express.. clients.. with 2min gap between them.
Now look at the imac and check the network preferences.. did it pick up the correct IP from the TC? It should have router (gateway) and DNS all correct using dhcp.. if not check the connectivity light on the TC.. does it come on when you plug in the ethernet cord?
Open a terminal on the mac and ping the TC address. does it respond?
Give a few screen shots of how the TC is setup.. bridge, router and what IP it is running. Even just the summary page.