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add time capsule to existing network to make subnetwork (two routers?)

8698 Views 7 Replies Latest reply: May 21, 2012 9:19 PM by LaPastenague RSS
zjoxx Calculating status...
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May 20, 2012 11:21 PM

We have a modem/router (motorola) provided by isp to connect to internet.  Most devices connect to this wirelessly.  We just purchased an Airport + Time Capsule to create a subnetwork (add to existing network via ethernet cable), so that only a few devices can wirelessly connect to Airport + Time capsule to store time machine back up and to wirelessly print to one printer connected by usb to Time Capsule.  When I select "I want to add to existing network" the motorola only shows up as a wireless, can't see the wired option.  I tested that the ethernet cable works and connected to one port on motorola and WAN on Time Capsule.  How do I tell Airport + Time Capsule to connect to motorola modem/router via the ethernet cable?  I think I want it to connect via cable because I don't want the Airport to replace the existing router, rather I want to end up with two routers (one for entire network, and second one just for subnetwork). 

Thank you.

  • LaPastenague Level 7 Level 7 (32,590 points)

    You will have to double NAT.


    Make sure the router you connect to the Motorola.. sorry I am unsure if it is the TC or airport being extreme??


    That it has a totally different IP address. So if Motorola happens to be 10.0.x.x then you should reset the TC or airport to 192.168.1.x for example.


    Plug into WAN port of the TC or airport.. the other device should then be plugged into the other and set in bridge mode.. that will ensure they are both part of the same network.

  • LaPastenague Level 7 Level 7 (32,590 points)

    Ok, your question confused me with the airport and TC as if it is two things not one.

    when I connect the ethernet cable to TC, why doesn't modem/router show up in connect to list?  Or if wrong list, where should I look, to select, to get it to "see" what it is connected to by ethernet?

    Are you using v6 in Lion utility? I am using SL with 5.5 utility. There is no such place that I can find. (You will do better downloading and using v5.6 for Lion anyway).


    On the manual setup.. summary page it will show the IP you get on the WAN port. From default settings this will all work properly.. there is nothing you need to do.

    Plug ethernet from modem router to TC wan port. When you do the TC will get an IP.

    If you open the internet tab, you can see Connect using.. ethernet. Just leave that. and everything else on auto.

    For connection sharing, you still need to share a public IP.. although TC will complain you are not using public but private IP.. there is nothing you can do about that. Just set the TC to ignore the error double NAT.





    When I began installation, I plugged everything in, then plugged in power.  I opened Airport Utility, and followed on-screen instructions, but when selecting "connect to existing network with ethernet cable" my modem/router doesn't appear in the list.


    Do not use connect to existing network.. that will bridge the TC which you don't want.


    You have to use the existing network as if it is public network. And stuff behind your TC is private.





    If I set the TC to bridge mode, won't it "take over" all router activity, and the first group of computers won't be able to connect directly to motorola? (I don't want this first group of computers to be able to connect to the TC).

    Also, I don't want the TC to connect to the motorola wirelessly.)

    If you set the TC to bridge it will not route at all... it will become a client of the existing network. And all IP addresses will be taken from the Motorola.. you will have one flat network, which is what usually people want.


    If you are still struggling.. do this.

    1. Tell me the IP address the existing Motorola is passing to the clients. Your one big issues here is making sure they are in fact on two different subnets.


    2. As long as condition of 1 is fulfulled this will work at default setting. Reset the TC by holding down the reset for 10sec.

    Plug Lan motorola to WAN TC.

    Plug a computer into the TC to do setup.

    Set up as if you have public IP on wan. Tell TC to ignore double NAT.

    Set wireless and TC names as you want.

    Now test internet.. on a client computer on the TC. it should work fine. At least for everything that doesn't need interactive connection.


    3. You can improve things by using DMZ in the Motorola to the TC. That alleviates at least some of the issues that arise with double NAT.

  • LaPastenague Level 7 Level 7 (32,590 points)

    zjoxx wrote:


    thank you, I will try this.  To be more clear, I think I am wanting to use the TC as a switch (not router) to connect two segments of our LAN, and use it as a wireless Print Server, and Storage.

    I am using AU 5.5.3 on a wired MacMini OS Leopard, to set up.  (though the laptops do have Lion.)

    Do you realise this is the opposite of your first post.. ???


    You stated in the first post you wanted a subnetwork.. and the TC to be second router.. now you don't want that at all. You want to have the TC as switch.


    IMHO.. for home network .. it is too hard to have multiple nets.. it just makes things messy. But there is no reason everything has to be on the one router as far as sharing wireless for instance.


    And the correct setup then is to bridge the TC.


    So you have


    Motorola--- Network via wireless and ethernet clients.



    TC-- in bridge.-- wired clients



    Wireless clients.


    Now what will happen.. with the TC in bridge.. but wireless using different SSID clients will join to TC that you setup for that SSID (wireless name in applespeak). But they will get IP gateway and DNS from motorola.

    All clients on the network can access all network resources.. but it is simply a case of how you set it up.


    As far as wired clients on the TC is concerned they are effectively on a switch plugged into the motorola..

  • LaPastenague Level 7 Level 7 (32,590 points)

      I do not want, or need to use bridge mode because that will push -all- network traffic through TC (not what I want).  I don't need to change my network map.

    Sorry you are incorrect. In bridge the only traffic going through the TC is traffic that belongs to its clients.. ie wireless and wired. No other traffic will pass through it.


    And there is no way for it to bridge the two sections of the network without it being either.. a bridge.. or a router in which case you will have double NAT issues.. Due to limitations of the gear you are using there is no other method.


    So if you really want two subnets.. ie on two different ip ranges.. where the devices connected behind the TC will not be available to the rest of the network.. then just use the TC in router mode. Try to use DMZ in the Motorola if possible as it will prevent some of the double NAT issues.


    Or bridge the TC.. and simply set it for use only by those devices that give the password to. ie no wireless from the Motorola can access the TC and no traffic will pass through it from anything else in the network.


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