Samsung TV and Directv won't connect to Airport TC

Hmmm Ok.. that is a lot of fun..

What model is your Motorola cable modem?

The new MBP will obviously be running Yosemite which I think is at least part of the problem..

How putting the TC in router mode helps the MBP work.. that is a bit hard to follow..

Let me suggest a simple work around to try first.

Assuming the Motorola is still running in router mode.. please turn the wireless back on.. there is no need to turn it off. The TC can work happily with the Motorola also having wireless running..

I do however recommend you fix its wireless channel so lets say channel 11. You can then reboot the TC and it will discover the wireless from the motorola and move channels to something that does not conflict.

Then see how the TV and Directtv go.

If that doesn't work out I have other things you can try.

Did you try and pick up the Motorola wireless from the TV, instead of the TC?? That might work where the TC doesn't.

When you put the TC in DHCP and NAT are you bridging the Motorola? If not the TC will throw up a double NAT error.. I would like to see the screenshots of the setup from your airport utility in the MBP that has issues.

Just post the summary will help. Both in bridge and in DHCP.. plus I would like to see the MBP setup for wireless and how it is different.

So this shot.. hover your mouse over the connection to get the extra details.. in my case it is the MAC address 28:37 etc.

Then the shot from your computer wireless network settings.

I want you to make sure you have IPv6 set to Link-Local only.. not automatic.

You might need to give me the DNS value as well.. although you can just copy and paste that one.

I want to see it both when the TC is bridged and when the TC is router.

There is another way to do the setup using static IP which might help.. but give me this info first.

As it stands, you have two devices on the same network, both trying to act as routers for the same network. Not a very good way to try to run a network, since a basic networking rule is to try to avoid a double router setup if possible. I can't recall a situation where a two router setup ever worked better than a correct network setup of having one router control the network.

AirPort Utility wisely tells users to place the AirPort router in Bridge Mode when a double router, or Double NAT, as it is known, situation exists on a network. I have to wonder about the advice to ignore the Double NAT error.....which strangely seems to have come from Apple support....in direct conflict with Apple's own AirPort Utility application.

As you note, everything was working fine with one router running the show with the Time Capsule in Bridge Mode..... until you had the issue with the new Mac trying to connect. There are major bugs in Yosemite, which are likely the cause of the problems when you had difficulties with the new Mac.

We've all had difficulties with Yosemite.....the worst operating system that Apple has ever introduced.

LaPastenague has good advice for you.

What makes the difference that being in bridge mode makes my MBP sporadically lose internet connection, but nothing else does?

Yosemite, most likely. it might work OK on one device, but act up on another. I can't get it to behave on either of my Macs though.

Apple care person told me this didn't matter.

That is amazing. There must be new networking rules that Apple has devised, but not told us about. Yet, other Apple support documents continue to advise users that they must not have a Double NAT on their network for things to work correctly. Example below:

Turn off NAT on one of your devices

If you’re using your modem as a router, or if you’re not using an Apple router, review the product documentation to see how to turn off NAT.

If you’re using an AirPort Base Station and you can’t turn off NAT on the modem or router, run the base station in bridge mode to turn off NAT:

1. From the menu bar, choose Go > Utilities, and double-click AirPort Utility.
2. Select your base station and click Edit in the pop-up menu.
3. Click the Network button and select Router Mode: Off (Bridge mode).
4. Click Update to restart the base station.

Not sure whether to laugh or cry.

But, let's get LaPastenague's take on this.

See edit above.

Soon, you may have to decide who you want to believe, and then stick with them.

Just so you know I agree with Bob.. double NAT is a problem.. perhaps only some of the time.. it causes websites to not completely download, it causes interactive stuff to not work.. it causes little problems that are then hard to figure out all along the way. You can get away with it but shouldn't.

So it is much much better to work correctly..

But it is clear it seems that Apple's network guys have given up.. and are now prepared to give bad advice to get people off the line.

Thanks for your screenshots btw.. excellent.. and easy to see.

I do want you to change the MBP to link-local only for IPv6 not automatic.. this is one of the things that leads to problems.

I think your setup is a good one to try using a static IP setup.. and see if we cannot solve both problems at once.

I cannot show you how to setup the motorola as I don't have one but I think you can do it fairly easily.

This has been working very well for me.

Here is what I have been using to avoid bridge. But at the same time to get the Airport or Time Capsule.. to control clients.

Set the main router IP range to something less than the whole range..

Let me use my actual setup.

At the moment I have a main router.. it is setup with

I set the DHCP range to a bit less than normal.

That leaves me a few IP addresses down low for devices that I might want to use directly on the main router, eg printers.

Then I can set the TC to use static IP. So I choose the next address from the main router.

In your case it would be 192.168.0.201

Put in the router address, this is more normally called GATEWAY..

in your case it will be 192.168.0.1,

And also use your ISP dns servers direct.. you can pick these up from the Motorola. You can also use a google public IP if you like, eg 8.8.8.8

Set Network to DHCP only.. and set a suitable range for you clients. You can use all the addresses between wherever you stop on the motorola and 192.168.0.254. I have a smaller range for my purpose.

In your case you can use 192.168.0.202-192.168.0.254

I have the lease time set very short 1hr in both the main router and the TC.

Then setup wireless to create a wireless network.

Then check on the computer.

The wifi is getting the IP and DNS info from the TC.

The computer shows as getting IP from the TC.

So this setup might work for you and stop the problem.

Should I go ahead and turn off the NAT on my cable modem or wait until Lapastenague replies?

Simply turning off the NAT on the cable modem/router will not make it a modem. See more detail below.

LaPastenague's method will avoid the Double NAT error, so that is one way to go and certainly worth a try if you do not have any other options.

Another way to go might be amazingly simple......ask your Internet Service Provider (ISP) if you can swap out the SB6850 modem/router, which is also called a gateway for a simple, bridge mode modem.

A simple bridge mode modem will allow you to run DHCP and NAT on the AirPort, so it will be in charge of your network. It will look something like this:

While a modem/router or gateway looks something like this:

Yet another option that might work is to set up your SB6850 in pure bridge mode, or it might be called modem mode. Some modem/routers can be setup to operate just like a simple bridge mode modem. Your ISP will likely not be thrilled to discuss this option with you, because it would involve more phone time for them. But, this could be a possibility if your ISP does not offer a simple modem option, or they won't allow you to use your own modem.

In my case, my ISP pushed hard for me to use their modem/router (for $8 a month), but I elected to buy a simple modem, which paid for itself in about 8 months.