self assigned IP address

You need to give us the whole network layout.. what modem do you have, make and model please?

Is it a bare modem or a gateway/router?

When you setup the new AE did you setup router or bridge mode? We need the exact setup, so a few screenshots from the airport utility tells thousands of words.

You can use a manually set IP in the computer.. that is a nuisance for a laptop but I suspect you don't cart the Mac Pro around with you much.

The reason you have to do it is due to wrong setup of the two routers.. perhaps 3 routers including the modem.

Thanks for the shots.. makes life so much easier.

Your old Extreme is in router mode.. but it should actually be bridged.. this is giving you a Double NAT error.

The correct setup then would be both the new and the old AE routers in bridge.. it little matters which goes first.. old new or new old.. the effect is much of a muchness.. although we do find the AC model WAN port less than reliable.

So reset both AE to bridge.. (router bridge that is) and set both to create a wireless of the same name and same password / security settings. You must not mix ethernet with extend wireless... that is big no no.

The alternative to this setup is to change the Westell modem to bridge and use PPPOE client on one of your AE.. then the second one would be in bridge.. however both still create a wireless network.

Either setup works pretty well the same.

When you do the setup.. due to Yosemite being a network doggie..

I recommend the follow for setups.

Start from full factory reset. Otherwise you get network errors.. reset both AE to factory and setup one then the other.

Factory reset universal

Power off the AE.. 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 AE 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.

Then redo the setup from the computer with Yosemite.

1. Use very short names.. NOT APPLE RECOMMENDED names. No spaces and pure alphanumerics.

eg AEgen6 and AEwifi for basestation and wireless respectively.

2. Use all passwords that also comply but can be a bit longer. ie 8-20 characters mixed case and numbers.. no non-alphanumerics.

3. Ensure the AE always takes the same IP address.. Think about this later in your case but stability on Yosemite with changing IP is poor due to the dog like nature of its DNS app.. about to be changed in the next patch release btw.

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..

5. 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.

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.

I have had this problem on and off for months. The connection to the router is fine one moment then is lost and self assigns. I then turn off wifi and turn on (sometimes a few times) and eventually it reconnects. Only to then disconnect a few moments later. Only happens on the mac (os x yosemite) . Ipad, iphone and windows PCs are all fine to the problem is not the router but os x on the mac.

I have found what seems to fix for me - in WiFi settings go to advanced and go to TCP/IP then switch IPv6 to Linked Local- this sort of fixed it for me but not completely. What I really needed was to switch IPv6 off altogether. To do this I had to run in terminal mode

1. Open Finder
2. Click on Applications
3. Click on Utilities Folder
4. Double Click on Terminal.app

now type in command

networksetup -setv6off Wi-Fi

That's it.

If you now go back to wifi settings and to the advanced setting in network and the TCP/IP header you will see IPv6 is off - and if you want can now be set on again manually at that screen - but now crucially you have an off option.

The only downside I think is that air drop might now not work - I don't use it anyway.

Thank you GM_Mac.

I received this message tonight even though IPv6 is set to local only (has been for years) but I had DHCP addresses that worked tonight and even manual addys that were working. I only saw this in between not having the various tabs in the Networking-Advanced panel not respond to mouse clicks intermittently. Weird.

As soon as I totally disabled IPv6 the message went away. Maybe whatever is going on with that DNS bug somehow started. I just wondered if there were more problems unseen with that error being displayed. No bridging or NAT issues between router and AP either.

If anyone knows actual system information regarding what triggers that manual IP message or the related DNS bug I'd like to see it or the bug report. Thx