How to tell if router or cable modem is the problem with bad internet?

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Level 1

16 points

How to tell if router or cable modem is the problem with bad internet?

I have intermittent internet problems at my home. The internet goes off for very brief periods, then back on many times a day. Usually bunched up in various periods of time. Then sometimes rather than being down for maybe a the normal 15-30 seconds, it might last 5-20 minutes. And there are also periods of hours sometimes where the speed is VERY slow.

When it's not working at all, Airport Utility looks like the following screenshot, with the Internet orange and the other devices green. Sometimes, it only shows the Internet icon and light, with nothing else below it. If the internet is just very slow (and I mean really slow, like 2 minute page loads if at all), everything is green including the Internet icon.

It's Charter Cable, with a Surfboard modem, connected to an older model Airport Extreme (in non-wireless mode), which is connected to three Airport devices you can see in the screenshot. It all has been working okay for 8 years, but these problems have been occurring the last few months. I've since replaced the cable modem for a brand new one, I've reset the Airport Extreme to factory settings and tried all sorts of other things.

It's not the wireless aspect, as I can plug a computer into the ethernet wall jack and it has the same problems.

So here is what I want to know: is there a way that I can tell if it's the Airport Extreme or if it's Charter Internet being flaky? (I know it's not the cable modem as it's doing the same thing as before I replaced it.) I'd just like to isolate the problem. I don't want to succumb to calling Charter yet, as we all know the run around I'm going to get before any tech would come to my home, and they'll never admit to having flaky internet.

I bought a Thunderbolt to Gigabit Ethernet Adapter so I can plug my Macbook Air right into the cable modem, bypassing the Airport Extreme, but the internet is not staying down long enough for me to get to it, plug it in and reboot the cable modem. Frustrating.

Posted on Jul 31, 2016 5:41 PM

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Answer 1

Bob Timmons

Level 10

186,086 points

Aug 1, 2016 7:07 AM in response to slobizman

Suggest that you connect the MacBook Air directly to the modem, connect the Mac to the Internet, and keep tabs on the MacBook Air from time to time over at least a full day. A few days would be even better, if possible.

If the connection stays solid during your "test", based on the other information that you have provided like......

connected to an older model Airport Extreme

and

It all has been working okay for 8 years

The first thought that comes to mind is that the useful life, on average, for the AirPort routers is about 5 years. That's about when the power supply, on average, starts heading downhill. Momentary drops start occurring, and the drops will increase in frequency as time goes on.

It's about a $20 gamble, but you might consider replacing the outboard power supply for the AirPort Extreme to see if that provides any help. This won't do anything for the internal power components inside the AirPort of course.

http://www.ebay.com/itm/ORIGINAL-OEM-APPLE-AIRPORT-EXTREME-BASE-STATION-POWER-SU PPLY-AC-ADAPTER-A1202-/370810566512

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Answer 2

slobizman Author

Level 1

16 points

Aug 1, 2016 7:45 AM in response to Bob Timmons

Thanks so much for your thoughts.

"Suggest that you connect the MacBook Air directly to the modem, connect the Mac to the Internet, and keep tabs on the MacBook Air from time to time over at least a full day. A few days would be even better, if possible."

It's not really practical, due to logistics, to do this. But let me ask you this: can I put a splitter of some sort coming off the cable modem, and have one cable going into my Airport Extreme to run my network, and the other cable going into a spare macbook pro I have that I can keep connected there on the floor (and maybe run a continuous Ping to google.com or some place (see discussion below)? Or would the splitter hurt the signal too much? (I don't know anything about splitters, obviously).

The first thought that comes to mind is that the useful life, on average, for the AirPort routers is about 5 years. That's about when the power supply, on average, starts heading downhill. Momentary drops start occurring, and the drops will increase in frequency as time goes on.

Yes, that's certainly a strong possibility. It's a 5th generation Airport Extreme. I could get the power supply, but I have no problem paying for even a new (used) 5th gen Airport Extreme. I see there are some on ebay and Amazon. Too bad I can't get a new one, but maybe I can get a refurbished one for a hundred buck or so. It is very often just the power supply?

(EDIT: Above paragraph edited: it DOES have a power supply when I originally wrote it did not).

I understand it would be better to buy a current generation Extreme, but the new form factor will not fit into my in-wall case that stores all my networking stuff and wiring. It's unfortunately an inch to wide, which really ***** for me.

But I tried something last night...

I read up on how to test connections and I decided to run a continuous Ping from my macbook air, connected directly to my cable modem. I ran it from 11:30pm to 6:30am this morning, pinging www.google.com. The results showed five problems that all looked like this, with 2-5 timeouts each.

ping: sendto: Network is down

Request timeout for icmp_seq 1715

Request timeout for icmp_seq 1716

Request timeout for icmp_seq 1717

The successful pings seemed to have times mostly in the 17-19ms range.I There were some outliers in the 20-30ish range, but a small number of them.

Is having five occurrences of this over a 7 hour period unusual (and it was a slow time on the web, being overnight)?

Note: With my normal network back up this morning, I'm pinging google.com from my wirelessly connected macbook air for the last hour, an zero issues. That's what makes it so hard to test over short periods -- it comes and goes. I've just added a second Terminal window to Ping my Extreme, to compare the two when there is a problem, but I suppose that's not going to tell me anything since if the Extreme doesn't connect then the other Terminal window pings won't be connecting to google.com.

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Answer 3

Bob Timmons

Level 10

186,086 points

Aug 1, 2016 9:20 AM in response to slobizman

can I put a splitter of some sort coming off the cable modem, and have one cable going into my Airport Extreme to run my network, and the other cable going into a spare macbook pro I have that I can keep connected there on the floor

This will depend on the type of modem that you have. If you have a simple modem (it will have only one Ethernet port, like the example just below), then you cannot "split" the signal.

If you have a modem/router (it will have at least four Ethernet ports, similar to the example below), then you could connect the MacBook Air using a spare Ethernet cable to one of the LAN <---> ports. Be sure to turn off the wireless on the MacBook Air, so that you will know that you are using a wired connection. The Ethernet connection can be any length that you want.

If you are not sure what type of modem that you have, post back with the make and model number of the device. Please do not post private information, like a serial number. We only the need the make and model number.

It's a 5th generation Airport Extreme

Then, it cannot be 8 years old. The 5th Gen was discontinued in June 2013, so it is at least 3 years old, and as much as 5 depending on when it was originally purchased.

If you are considering replacing the 5th Gen, some resellers will offer up to a 30 day return privilege, so if a "new" Extreme behaves the same as the existing product, you are only out a bit of time and possibly some shipping charges.

There are a number of sources selling 5th Gen products on the Internet, some re-furbished. It's possible that a reseller might have a "new" 5th Gen, but it has been sitting on the shelf for at least 3 years.

There is also another possibility that might be causing the connection problems, and that is that most Internet Service Providers (ISPs) are in the process of adding and changing over to IPv6 type of connections. While the transition is going smoothly for some providers, others are having various issues.

Unless you have received specific instructions from your ISP on how to configure the IPv6 settings on your AirPort Extreme, my recommendation would be to set the IPv6 connection to Link Local Only to see if that helps with the connection issue. If it does, then your ISP is having some implementation problems that they are not telling you about.

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Answer 4

slobizman Author

Level 1

16 points

Aug 1, 2016 9:30 AM in response to Bob Timmons

"This will depend on the type of modem that you have. If you have a simple modem (it will have only one Ethernet port, like the example just below), then you cannot "split" the signal."

I have a simple cable modem, just oneEthernet port.

"Then, it cannot be 8 years old. The 5th Gen was discontinued in June 2013, so it is at least 3 years old, and as much as 5 depending on when it was originally purchased."

I'm very sorry, it's not 5th gen, it's just a square format one that looks like the fifth gen. So it's whatever the gen is that was out as off late 2008. (Thanks for your patience with my screwups!) So, that's good news: buying a fifth gen, even completely used, will be less used than mine.

...my recommendation would be to set the IPv6 connection to Link Local Only...

I checked and this is my current setting already.

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Answer 5

Bob Timmons

Level 10

186,086 points

Aug 1, 2016 9:32 AM in response to slobizman

Then, please make sure that your Mac is set to Link Local Only as well.

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Answer 6

slobizman Author

Level 1

16 points

Aug 1, 2016 9:50 AM in response to Bob Timmons

Okay, it was set to Auto, and I changed the setting to Link Local Only. I did it through System Preferences/Network... Is that right? Here's the screenshot:

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Answer 7

Bob Timmons

Level 10

186,086 points

Aug 1, 2016 11:28 AM in response to slobizman

That is correct. If you plan to connect using Ethernet on the Mac, then you will need to run through the same type of procedure starting with highlighting the Ethernet icon on the left panel of the main network page.

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Answer 8

slobizman Author

Level 1

16 points

Aug 1, 2016 12:33 PM in response to Bob Timmons

I did some reading to understand what this IPv6 issue is and this article seems to explain it. Is this what you are talking about?

If so, is there any reason that a square format Airport Extreme will not handle this fix as well as the latest version Extreme? The reason I ask is that I'll likely buy a another 5th Gen Extreme (I can get one for about $40 on ebay) even if my problems subside; even just to have for a replacement for later if I need it. I really don't want to have to buy the latest model desktop Extreme as it doesn't fit where I need it to put it. But, if it handles this Link-local only stuff better than the older model, I'll find a way to make it fit.

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Answer 9

Bob Timmons

Level 10

186,086 points

Aug 1, 2016 1:00 PM in response to slobizman

The article has some good basic information, but may not be clear on a "fix" regarding Link Local Only. The Link Local Only setting disables the IPv6 Internet connection that is coming from the Internet Service Provider, but allows IPv6 connections over your "local" network.

So, when you use Link Local Only on a AirPort router, you will not be receiving the benefit of IPv6 connections from the Internet. For most folks, that's OK since they would rather have a stable connection using IPv4 than a goofy one involving IPv6, which is not really of much use now anyway.

If so, is there any reason that a square format Airport Extreme will not handle this fix as well as the latest version Extreme?

Looks like you have already answered your own question. Your current 5th Gen has settings for IPv6 Link Local Only, so any other 5th Gen will as well......assuming that it is running up to date firmware.

Things are going to continue to be very confusing over the next few years, I am afraid.

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Answer 10

slobizman Author

Level 1

16 points

Aug 1, 2016 1:00 PM in response to Bob Timmons

Thanks. I understand now. You have a lot of patience. 🙂

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Answer 11

slobizman Author

Level 1

16 points

Aug 3, 2016 10:20 AM in response to Bob Timmons

I was going to write this morning how great my connection has been since making the Link Local Only change. I have not had any problems whatsoever. It's been great! Thank you!!

Then this morning I had a minor event. My connection went out and I looked at Airport utility and saw that all my devices were down, starting with the Airport Extreme that connects to my cable modem. And they looked different than just showing the orange dot, they had the warning triangle and when clicked, no Edit button to go into the devices. But it came back up in just a few minutes.

So in looking around after that, I went into my cable modem via 192.168.100.1 and looked at the logs. And then I saw the only errors ever recorded for the cable modem, all bunched within a few minutes. I'm showing this below. What's interesting though is that these events occurred a few hours before the time when I saw my connection go down. (Note: my modem is only about a month old, from when I replaced old one.)

Just a random issue, timed to screw with me now that my connection is smoother? 🙂 Or could it be something to do with changing devices to Link Local Only?

Time	Priority	Code	Message
Aug 03 2016 05:46:30	6-Notice	N/A	MDD Recovery following MDD Loss;CM-MAC=20:3d:66:04:07:fd;CMTS-MAC=00:01:5c:6d:22:5f;CM-QOS=1.1;CM-VER=3.0;
Aug 03 2016 05:46:30	5-Warning	T202.0	Lost MDD Timeout;CM-MAC=20:3d:66:04:07:fd;CMTS-MAC=00:01:5c:6d:22:5f;CM-QOS=1.1;CM-VER=3 .0;
Aug 03 2016 05:46:30	6-Notice	N/A	MDD Recovery following MDD Loss;CM-MAC=20:3d:66:04:07:fd;CMTS-MAC=00:01:5c:6d:22:5f;CM-QOS=1.1;CM-VER=3.0;
Aug 03 2016 05:46:30	5-Warning	T202.0	Lost MDD Timeout;CM-MAC=20:3d:66:04:07:fd;CMTS-MAC=00:01:5c:6d:22:5f;CM-QOS=1.1;CM-VER=3 .0;
Aug 03 2016 05:46:30	5-Warning	N/A	DS Partial Service Fallback: MDD Lost-> CM in DOCSIS 3.0 Recovery Mode ;CM-MAC=20:3d:66:04:07:fd;CMTS-MAC=00:01:5c:6d:22:5f;CM-QOS=1.1;CM-VER=3.0;
Aug 03 2016 05:46:30	5-Warning	T202.0	Lost MDD Timeout;CM-MAC=20:3d:66:04:07:fd;CMTS-MAC=00:01:5c:6d:22:5f;CM-QOS=1.1;CM-VER=3 .0;
Aug 03 2016 05:46:30	5-Warning	N/A	DS Partial Service Fallback: MDD Lost-> CM in DOCSIS 3.0 Recovery Mode ;CM-MAC=20:3d:66:04:07:fd;CMTS-MAC=00:01:5c:6d:22:5f;CM-QOS=1.1;CM-VER=3.0;
Aug 03 2016 05:46:30	6-Notice	N/A	MDD Recovery following MDD Loss;CM-MAC=20:3d:66:04:07:fd;CMTS-MAC=00:01:5c:6d:22:5f;CM-QOS=1.1;CM-VER=3.0;
Aug 03 2016 05:46:30	5-Warning	T202.0	Lost MDD Timeout;CM-MAC=20:3d:66:04:07:fd;CMTS-MAC=00:01:5c:6d:22:5f;CM-QOS=1.1;CM-VER=3 .0;
Aug 03 2016 05:46:30	5-Warning	N/A	DS Partial Service Fallback: MDD Lost-> CM in DOCSIS 3.0 Recovery Mode ;CM-MAC=20:3d:66:04:07:fd;CMTS-MAC=00:01:5c:6d:22:5f;CM-QOS=1.1;CM-VER=3.0;
Aug 03 2016 05:46:30	6-Notice	N/A	MDD Recovery following MDD Loss;CM-MAC=20:3d:66:04:07:fd;CMTS-MAC=00:01:5c:6d:22:5f;CM-QOS=1.1;CM-VER=3.0;
Aug 03 2016 05:46:30	5-Warning	T202.0	Lost MDD Timeout;CM-MAC=20:3d:66:04:07:fd;CMTS-MAC=00:01:5c:6d:22:5f;CM-QOS=1.1;CM-VER=3 .0;
Aug 03 2016 05:46:30	5-Warning	N/A	DS Partial Service Fallback: MDD Lost-> CM in DOCSIS 3.0 Recovery Mode ;CM-MAC=20:3d:66:04:07:fd;CMTS-MAC=00:01:5c:6d:22:5f;CM-QOS=1.1;CM-VER=3.0;
Aug 03 2016 05:46:29	6-Notice	N/A	MDD Recovery following MDD Loss;CM-MAC=20:3d:66:04:07:fd;CMTS-MAC=00:01:5c:6d:22:5f;CM-QOS=1.1;CM-VER=3.0;
Aug 03 2016 05:46:29	5-Warning	T202.0	Lost MDD Timeout;CM-MAC=20:3d:66:04:07:fd;CMTS-MAC=00:01:5c:6d:22:5f;CM-QOS=1.1;CM-VER=3 .0;
Aug 03 2016 05:46:29	5-Warning	N/A	DS Partial Service Fallback: MDD Lost-> CM in DOCSIS 3.0 Recovery Mode ;CM-MAC=20:3d:66:04:07:fd;CMTS-MAC=00:01:5c:6d:22:5f;CM-QOS=1.1;CM-VER=3.0;
Aug 03 2016 05:46:28	5-Warning	T202.0	Lost MDD Timeout;CM-MAC=20:3d:66:04:07:fd;CMTS-MAC=00:01:5c:6d:22:5f;CM-QOS=1.1;CM-VER=3 .0;
Aug 03 2016 05:46:06	3-Critical	T05.0	SYNC Timing Synchronization failure - Loss of Sync;CM-MAC=20:3d:66:04:07:fd;CMTS-MAC=00:01:5c:6d:22:5f;CM-QOS=1.1;CM-VER=3.0;
Aug 03 2016 05:38:56	5-Warning	Z00.0	MIMO Event MIMO: Stored MIMO=-1 post cfg file MIMO=-1;CM-MAC=20:3d:66:04:07:fd;CMTS-MAC=00:01:5c:6d:22:5f;CM-QOS=1.1;CM-VER=3 .0;

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Answer 12

Bob Timmons

Level 10

186,086 points

Aug 3, 2016 10:32 AM in response to slobizman

Might help to know which device has a MAC Address of 00:01:5c:6d....., and which has an address of 20:3D:66:04......

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Answer 13

slobizman Author

Level 1

16 points

Aug 3, 2016 2:06 PM in response to Bob Timmons

Wow, this is really strange. None of my devices have MAC addresses that match those in the log. I used the Fing app to show me all my devices their their MAC addresses.

Here are two screenshots of my MAC addresses from Fing's finding. (They overlap a bit).

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Answer 14

Bob Timmons

Level 10

186,086 points

Aug 3, 2016 2:27 PM in response to slobizman

Then, this tells me that the modem is very likely having difficulty maintaining a reliable connection with the router(s) at your ISP. The ISP will of course deny this if you call them, since they will likely say something like "everything looks good from here".

This is why I suggested that you connect your MacAir directly to the modem for a day or two and check the connection from time to time, or check the logs in the modem. You take the AirPort Extreme entirely out of the equation this way and narrow down the possibilities to your modem and ISP.

If you see similar issues to what you have already seen during your "test"....with the AirPort Extreme not even on the network.... then you know that you have a modem / ISP issue, not an AirPort Extreme issue.

If things work perfectly during your "test", then the focus shifts to the AirPort Extreme. About all that you can do is try another AirPort Extreme to see if it will behave better.

If the second AirPort Extreme acts up like the first, then you likely have a modem / AirPort incompatibility issue, and will have to try another brand of modem or another brand of router.

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Answer 15

slobizman Author

Level 1

16 points

Aug 3, 2016 2:32 PM in response to Bob Timmons

Okay, thanks again. Considering the price of a used 5th gen Airport Extreme being so low, I am going to just buy one and replace it and go from there. As you said earlier, it's useful life is about gone anyway. Then, if there are problems, and those problems are too frequent I'll go down that dreaded route of calling Charter. But given I've had such good luck (other than this one issue) since you told me about Link Local Only, I'm hoping it will be all "good enough." I've had problematic internet for 20 years through various ISP's and two different locations, so what else is new? 😟

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