Use Time Capsule over ethernet only?

Question

Running Mavericks.  Have a 2 TB surplus Time Capsule that I would like to use to back up an iMac using an ethernet cable between the iMac and the TC rather than wirelessly.  (I am trying to avoid yet another Wi-Fi device on my Airport Extreme network and the reduced performance that comes with extending a network.)  Indeed I have made this work per Bob Timmons prior posts by hooking the TC to both the iMac and temporarily to the Airport Extreme via ethernet cable.
Due to house configuration, it is not possible for me to permanently run ethernet between the Airport Extreme and the TC.  In my experimenting, after setup I unhooked the connection between TC and Airport Extreme and the iMac and I thought the iMac was continuing to  recognize the TC and backup to it over ethernet, but after a re-start I cannot get that configuration to work again.
1.     Do I understand that the design of the TC is such that it cannot be used as an attached ethernet hard drive for Time Machine backups unless it is at all times also connected to a [Airport Extreme] router?
2.     If No. 1 above is true, is there any wireless configuration of the TC that would allow for the benefits of ethernet connection to the iMac but not have the permanent router/TC ethernet connection?
3.  Finally, if I am out of luck on ethernet only from the iMac, since I don't use the iMac wirelessly for anything, can a create a new network with the TC and have the iMac wirelessly connect with that without a permanent router connection?
Thanks very much

Answer 1

Thanks for your insightful questions and comments!
If you have an Ethernet cable connected to the iMac, the iMac will default to the Ethernet connection, even if wireless is on at the iMac.So, if you want to backup the iMac over wireless, you will have to manually disconnect the Internet Ethernet cable at the iMac every time that you want to back up the iMac. Once the backup over wireless is completed, then you will have to connect the Internet Ethernet cable again to the iMac.
Is this true?  I was referring to the ethernet cable running between the iMac and the TC, not the main ethernet connection to my home network.  My entire goal here has been to simply hookup the TC to the iMac solely for backup purposes via ethernet.  However, you have convinced my I cannot do that without the TC also being connected to the Airport router at the same time., which I believe is not practical for the reasons below.  So again, assuming that the iMac is connected to the TC via the TC's separate wireless network, is not the ethernet cable between iMac and TC not used - or will the iMac communicate to the TC via faster ethernet  instead of defaulting to the slower wireless network?
The iMac is about 12" away from the iMac and I am not trying to hide it - I just want to use it as a ethernet backup disk!
I guess I'm wondering why.....if the Mac connects to the AirPort Extreme using Ethernet.....you cannot connect the Ethernet cable from the AirPort Extreme to the Time Capsule first, then connect another Ethernet cable from the Time Capsule to your iMac.
Then, the iMac is always connected using Ethernet, and you won't have to use wireless at all. You can backup over the much faster Ethernet connection. Everything will stay connected all the time.....no cable disconnecting.....and you have the best performance as well.
Good question!  My newly remodeled house has an ethernet network wired throughout.  One ethernet outlet per room.  (The Airport Extreme router connects to a Comcast modem via the ethernet network, each in separate rooms.  I was able to connect the TC to the Airport router using an 80 foot temporary cable running between rooms.)  Maybe there is a way to have the TC  "share" the iMac single ethernet port in the room that I am not aware of?   Appreciate your thoughts.
But, again....If the TC and iMac will be close to each other....why mess with wireless and cable swapping when you can do everything over Ethernet, and always stay connected to the AirPort Extreme network.
You are preaching to the choir.  I don't want to use wireless at all for backup or even have it on for my iMac.  The lack of a connection between TC and Airport router is what seems to be stopping me.
The TC will create both a 2.4 GHz and 5 GHz network automatically. The iMac will look at both signals and choose the best with which to connect. If the iMac has line-of-sight, or is in the same room as the TC, then it will likely connect at the faster 5 GHz connection.
And here is the last puzzle.  Assuming that I cannot resolve the ethernet to router issue, I am today backing up to the TC (also connected via ethernet cable to iMac) via the separate WiFi network created by the TC.  The backup has worked several times today.  Despite this, Airport Utility reports that the TC cannot be found even though it was "previously part of the network."  Any ideas on that one?
Thanks