Sorry I really don't follow your question 1.
You ask a question and then state you know it isn't possible .. and that is correct. The TC must be plugged into the router by ethernet.. it cannot exist on the network joining by wireless.. not without severe issues and apple seem to have taken away that possible setup recently.. it is so bad we would never recommend it.
Your main question is access..
2. I have a cisco as main router and also a wireless repeater(tp link).. I'm planning to connect the time capsule with tplink
The best place for the TC is plugged into the cisco and working in bridge mode.. do not connect it via a wireless bridge or repeater, unless you intend to plug in by ethernet in the location where the TC is.
It is possible to get access to the TC.. but you need to set it up manually.. and ensure everything is working in the same domain.
What Cisco router do you have? What is its default domain? If you don't know what I mean by domain.. open the network utility in your Mac and run a netstat scan.
The result will look like this.
Internet:
Destination Gateway Flags Refs Use Netif Expire
default gargoyle.lan UGSc 10 2 en1
default 10.0.1.1 UGScI 8 0 en0
10.0.1/24 link#5 UCS 1 0 en0
10.0.1.1 90:84:d:e7:34:a7 UHLWIir 10 444 en0 1086
10.0.1.3 localhost UHS 0 0 lo0
127 localhost UCS 0 0 lo0
localhost localhost UH 0 15012 lo0
169.254 link#4 UCS 2 0 en1
rays-airport-extre 5c:96:9d:67:53:cd UHLSWi 0 6 en1 1090
tcgen4a.local link#4 UHLSW 0 3 en1
192.168.2 link#4 UCS 8 0 en1
192.168.2.35 0:30:6e:c8:a5:46 UHLWIi 0 1 en1 1086
xbox-systemos.lan 50:1a:c5:bb:1a:bb UHLWIi 0 1 en1 1086
nas-server.lan 0:11:41:30:14:bb UHLWIi 1 888 en1 1188
tcusgen3.lan 90:84:d:e7:34:a7 UHLWIi 0 1 en1 1086
minimeray.lan localhost UHS 1 4 lo0
192.168.2.201 b8:c7:5d:cf:63:77 UHLWIi 2 435 en1 1086
192.168.2.203 5c:96:9d:67:53:cd UHLWIi 2 281 en1 1088
192.168.2.219 b8:3e:59:78:6c:ca UHLWIi 0 1 en1 1088
gargoyle.lan 22:4e:7f:77:bc:f4 UHLWIir 11 1056 en1 1192
What is important to notice is the main router has name.. gargoyle.lan
And the Time Capsule Or at least one of them is tcgen4a.local
The very fact that these two items have different domain names makes things that little bit more difficult.
Especially with Yosemite which has broken DNS. No matter which OS you are running I recommend the following.. in your case you need to make sure everything in the network is bridged (except the main router) and you have only one IP subnet..
Mount the disk on the computer manually as per point 5 below..
When you mount by IP address it helps bypass the domain and the poor DNS issues..
However if at all possible connect to the TC by ethernet or wireless.. rather than other devices in the network.. as that leads to the least issues.
Start from a factory reset. No files are lost on the hard disk doing this.
Factory reset universal
Power off the TC.. ie pull the power cord or power off at the wall.. wait 10sec.. hold in the reset button.. be gentle.. power on again still holding in reset.. and keep holding it in for another 10sec. You may need some help as it is hard to both hold in reset and apply power. It will show success by rapidly blinking the front led. Release the reset.. and wait a couple of min for the TC to reset and come back with factory settings. If the front LED doesn’t blink rapidly you missed it and simply try again. The reset is fairly fragile in these.. press it so you feel it just click and no more.. I have seen people bend the lever or even break it. I use a toothpick as tool.
N.B. None of your files on the hard disk of the TC are deleted.. this simply clears out the router settings of the TC.
Setup the TC again.
Then redo the setup from the computer with Yosemite.
1. Use very short names.. NOT APPLE RECOMMENDED names. No spaces and pure alphanumerics.
eg TCgen5 for basestation and TCwifi wireless name.
If the issue is wireless use TC24ghz and TC5ghz with fixed channels as this also seems to help stop the nonsense. But this can be tried in the second round. ie plan on a first and second round of changes to fix this.. hopefully.. I will point out other steps that can be round2.
2. Use all passwords that also comply with 1. but can be a bit longer. ie 8-20 characters mixed case and numbers.. no non-alphanumerics.
3. If the TC is main router you can skip this point. This is only an issue when the TC is bridged.
Ensure the TC always takes the same IP address.. you will need to do this on the main router using dhcp reservation.. or a bit more complex setup using static IP in the TC. But this is important.. having IP drift all over the place when Yosemite cannot remember its own name for 5 min after a reboot makes for poor networking.
4. Check your share name on the computer is not changing.. make sure it also complies with the above.. short no spaces and pure alphanumeric.. but this change will mess up your TM backup.. so be prepared to do a new full backup. Sorry.. keep this one for second round if you want to avoid a new backup.
5. Mount the TC disk in the computer manually.
In Finder, Go, Connect to server from the top menu,
Type in SMB://192.168.0.254 (or whatever the TC ip is which you have now made static. As a router by default it is 10.0.1.1 and I encourage people to stick with that unless you know what you are doing).
You can use name.. SMB://TCgen5.local where you replace TCgen5 with your TC name.. local is the default domain of the TC and doesn't change.
However names are not so easy as IP address.. nor as reliable. At least not in Yosemite they aren't. The domain can also be an issue if you are not plugged or wireless directly to the TC.
6. Make sure IPv6 is set to link-local only in the computer. For example wireless open the network preferences, wireless and advanced / TCP/IP.. and fix the IPv6. to link-local only. Do the same for ethernet if you use it.
There is a lot more jiggery pokery you can try but the above is a good start.. if you find it still unreliable.. don't be surprised.
You might need to do some more work on the computer itself. eg Reset the PRAM.. has helped some people. Clean install of the OS is also helpful if you upgrade installed.
Tell us how you go.
Someone posted a solution.. See this thread.
Macbook can't find Time Capsule anymore
Start from the bottom and work up.. I have a list of good network practice changes but I have avoided Yosemites bug heaven.
Yosemite has serious DNS bug in the networking application.. here is the lets say more arcane method of fixing it by doing a network transplant from mavericks.
http://arstechnica.com/apple/2015/01/why-dns-in-os-x-10-10-is-broken-and-what-yo u-can-do-to-fix-it/
