Time Capsule won't backup if Modem (Motorola SB6121) attached

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Level 1

15 points

Time Capsule won't backup if Modem (Motorola SB6121) attached

Before I get into my issue, some quick background info is needed:

Back in early Dec I purchased a cloud based backup service. I have some 3TB of data. Comcast has a cap of 300GB else you will be billed. I called Comcast support and specifically asked if that includes both downloads and uploads. I was told downloads ONLY. So I started my backup selecting all data. Come end of Dec, Comcast advised me that I went over and billed me. I called them to say this was because of the false info I got from Comcast (turns out uploads do count). They wouldn't reverse this. I called corporate to get better service. On dec 29th a ticket was opened for this. I was initially told they wouldn't reverse it but soon changed their mind. While I was talking to their "CSA" rep I mentioned that when I got a new modem (SB6121) in Aug, customer service never removed my old Linksys and asked if he could do that as well. As a result of fixing these, the usage meter (how Comcast measures internet usage stopped reporting. Since Jan Comcast has been working on that.

Also I wanted to draw a quick description of the equipment I have and how connected:

Telephone pole has a wire that goes right into the modem (SB6121) directly (no splitters etc)

From the modem is an Ethernet cable that plugs directly into my Time Capsule (latest model (tower vs. flat one)).

From the Time Capsule there are 3 ports:

1) directly into my 27" Imac running Mavericks

2) directly into a WD mycloudmirror NAS device

3) Apple Tv

Issue/Troubleshooting: Starting approx. 2 weeks ago my Time Machine backups were failing with various messages. The popup from TM stated "invalid network username or password" In console log, I saw "authentication error (80)" (which I later found out is a general communication error on port 80

Working with Apple, it was discovered my 4 month old TC could be bad. So I swapped it out for a new one. When I tried to add the new TC I could not. I could see it, configure it. But when I tried to save/update settings it would time out with a generic "unknown error". Working with Apple we could not figure this out. Finally for giggles, I removed the modem (power and coax). I was then able to fully configure the TC via Airport. A backup kicked off. I connected the modem and walked away. Next am I saw that all subsequent backups failed with same errors as above. Working with Apple, they couldn't figure it out. So they collected data to send to their engineering. I was also put in touch with an Apple Sr networking advisor. I told him once I take the modem off all works fine. We tested and confirmed. He suggested I take the TC to a neighbors house and modem and from my Ipad using airport utility see if I can talk to and update the TC. If this works the TC is fine and its a modem issue, else its a TC issue (which is unlikely since it was just bought new 2 days ago). Low and behold on my neighbors modem, I could configure the TC without incident. But once back in my home with the modem, NOTHING - can't update the TC nor do backups.

While I was waiting to hear from Apple engineering, I thought I would check with Comcast to see if there had been any firmware updates pushed out. Comcast DENIED me support stating I no longer had an account with them simply because they saw no equipment on my acct. I logged in and sure enough there was nothing connected. So the back in Jan the Comcast person who was trying to fix my usage meter and I asked him to remove the Linksys, seems to have removed everything. I called Comcast corp again and was put in touch with an escalations person. He stated it might not be a bad idea to swap out the modem as he was seeing a lot of timeout /disconnects. I got a new modem and same issue.

I worked with Apple and did the following additional troubleshooting:

Moved TC to another Imac (running Mtn Lion) - same issue; which rules out the mac hw and the OS along with airport utility

Swapped TC - same issue

Swapped Modems - same issue

Connected NEW cable - same issue

Hooked up to neighbors modem - works fine (btw they are on ATT Uverse as their modem and provider)

So in conclusion I and Apple have determined this is a modem/Comcast issue, possibly some signal or loopback - or something.

In Comcast's defense they are saying a modem should not be interfering like this. I would agree, but all above steps have proved the modem or ISP would be the best culprit in this.

If I connect the modem I can surf the net but not access TC nor backup. If I
remove the modem I can access the TC and backup but cannot surf.

Can anyone out there offer any suggestions, thoughts, hints, recommendations?

Thanks in advance

Posted on Feb 9, 2015 9:15 AM

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Answer 1

Feb 9, 2015 12:10 PM in response to DeputyDawg

The latest SB6121 and 6141 are definitely not compatible with the newest Apple routers.. for loads of people at least.

Just do a search here for those models..

My recommendation is simply buy a Zoom cable modem.. which seems to be much less of an issue..

Apple are having loads of problems with the new airport series.. AE and TC not working at all on the WAN port with lots of products.. So it is best just to avoid.. one or the other.

If you wish to use the SB6121, buy a different router.. and bridge the TC to it.. so you can use it just for backup and AP purposes.

You seem to have had an interesting run with Comcast.

What should have happened is that when they cut your account all internet connectivity should have stopped.

I suspect you got a local IP address.. 10.x.x.x which Comcast do use for control of modems.. and somehow you were still able to get some network access on this. However since the TC also uses 10.0.1.1 as its home address.. it would cease to route correctly and would give you major local network issues.

A lot of what happened simply should not.. that has added massive level of confusion to what was already several layers of problems.. !!

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Answer 2

DeputyDawg Author

Level 1

15 points

Feb 9, 2015 12:14 PM in response to LaPastenague

Interesting...

However, I have had the SB6121 in my env since Aug with NO issues. This all appeared to have started when Comcast started making changes on my account (ie usage meter, removing equipment). Everything was hunky dorey before then.

Oh btw, I have had the latest TC since I bought the new Mac which was June-ish time frame.

Again what has changed???

Also if you could please, explain this part of what you said. I'm not sure I follow:

"I suspect you got a local IP address.. 10.x.x.x which Comcast do use for control of modems.. and somehow you were still able to get some network access on this. However since the TC also uses 10.0.1.1 as its home address.. it would cease to route correctly and would give you major local network issues."

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Answer 3

Feb 9, 2015 12:13 PM in response to DeputyDawg

Yes.. I can well accept it.. but whatever they did put you in the same situation as many others.

Not everyone is affected.. some are.. what is happening is outside my pay grade.

Seems like Comcast and Apple Engineers are equally clueless though.

TC and Motorola 6121 or 6141 issues.

Use a cross over cable.

https://discussions.apple.com/thread/5048548?start=15&tstart=0

https://discussions.apple.com/thread/5187450

Many many threads.. if you do a search. Ever since latest version hardware and firmware revisions.

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Answer 4

DeputyDawg Author

Level 1

15 points

Feb 9, 2015 1:05 PM in response to DeputyDawg

Hey there

When you can could you please explain the part of your earlier statement about the IP address between modem and TC. I am not sure I understood that.

Also I did as you suggested, some google searches. Yes I found lots of hits, but their issues didn't seem to match mine.

When my SB6121 is connected I can surf allllll day and night long and it never drops. The problem is with the modem connected, Time Machine cannot backup to the TC. Once the modem is removed, TM can backup to the TC without an issue. However of course I can't surf.

Make sense?

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Answer 5

Feb 9, 2015 1:28 PM in response to DeputyDawg

When my SB6121 is connected I can surf allllll day and night long and it never drops. The problem is with the modem connected, Time Machine cannot backup to the TC. Once the modem is removed, TM can backup to the TC without an issue. However of course I can't surf.

Make sense?

Yes, and no..

The best way to solve something like this is to give me screenshots..

I need a screenshot of your Mac's ethernet connection when you are plugged into the SB6121 and everything is working lovely!!

So I can see.. IP address, subnet mask, gateway and DNS values.

I need to then see the same thing when you have power cycled the SB6121 (off for 15min at least).. with the TC plugged into it in router mode.. and the Mac plugged into the TC.

I then also need to see the airport utility info from the TC.

So I need to see the summary page.. ie this one.

Then I want you to click the edit button and give me the Internet tab and Network tab so I can see how you have the TC setup and what is happening.

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Answer 6

DeputyDawg Author

Level 1

15 points

Feb 10, 2015 12:05 PM in response to LaPastenague

Hey there,

Since yesterday there has been some progress on Comcast's side. I finally got to someone who seemed to have both the knowledge and the desire to help customers.

Whatever she did (which I think was as simple as a reset of my account (recall there was a bunch of changes - adds/deletes etc)), I now see a progress bar on my equipment. Granted there is no data usage yet (which does take 24+ hours to populate), but I do see the place where the progress bar would be.

When her and I spoke, she suggested powering off ALL equipment (modem include coax) for 30 mins. After that power up modem first and after it syncs up to Comcast then bootup TC and plug in ONLY the modem and to mac (leave out NAS and Apple TV). See if I can do a backup.

I did this and I was able to do a backup. However, I wasn't too excited since part of the symptoms were that an initial backup would work but all subsequent would fail. In between backups I tried to make some very simple changes to the TC via airport utility. NOPE - could not.

However, all backups ran without incident over night. When I get home I will disconnect the modem to see if I can then make changes to the TC. I may do the same power down steps only when I come up I may do a factory reset of the TC.

Anyways, I did gather some screen shots for you

Hope these help. Let me know if you need anything else

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Answer 7

Feb 10, 2015 12:20 PM in response to LaPastenague

In the Internet Options

Try setting the IPv6 value to something other than auto.. Comcast is giving you IPv6 addresses but they look strange..

Set to link-local only.

Also in the computer use IPv6 as link-local only.

Tell me if that fixes things. (Ignore my dynamic global hostname.. I was fiddling around).

In the computer for example wifi like this.

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Answer 8

DeputyDawg Author

Level 1

15 points

Feb 10, 2015 12:48 PM in response to LaPastenague

OK will do

I know on the Mac in network preferences we set IP6 to Link-Local

On your screen shot for internet options where you put in a host name of TC Gen4.local -- do I make up that name or does the TC/Airport utility do it or does it simply not matter what is there

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Answer 9

Feb 10, 2015 2:13 PM in response to DeputyDawg

Ignore the hostname.. as I commented .. I was just fiddling at the time I did the screenshot.. I have a whole folder of screenshots which I reuse otherwise it takes too long to redo the setup of the network over and over to help people but I should replace that one so people are not confused.. IPv6 is still a mystery to all of us.. as very few ISP use it and I am not used to looking at the values it is giving. Certainly the comcast values look odd. By using link-local you should be ok. But if it still causes trouble and if you can edit them, then I would recommend you remove the ipv6 values. The whole network will still work fine via the ipv4 settings.

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Answer 10

DeputyDawg Author

Level 1

15 points

Feb 10, 2015 3:05 PM in response to LaPastenague

DUDE you ROCK !!!!!!!

I had changed the network side to Link-Local but NOT on the airport side

I can now surf, backup, and make changes to the TC

I guess I'm still curious why this has been working for so long? I suspect Comcast did make some changes on their end (which they clearly did from my post). Maybe that combo did it....????

I still want to do some more testing, but so far it all works !!!!!!!!!

THANK YOU

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