sorry to ask this if it has already been answered, but have you tried a different router or something else network hardware wise over than your toshiba broadband modem?

Also, what type of config can you set up for this modem since it hands out IPs and such.

What happens if you assign it static information for the DNS and use DHCP for everything else?

No. Previously, had a router on the modem to share the internet connection, but the router started to fail, so it is gone.

I don't know if the modem is failing... very frustrating that network devices can partially fail- why is that?

I don't have another modem, and would like to try to be sure the modem is failing before seeking a replacement. (If so, I will look for some good recommendations!)


ISP => cable modem => Mac



It is not configurable.




I was concerned about DNS earlier when I first started getting these problems, and tried a static DNS entry. It slowed the DNS lookups slightly, the ISP DNS (blank in Network preferences) was faster, and had no effect on the other problems.

The problem is with the Mac getting internet connection, not DNS. If the Mac gets the remote ip address from the router, then the internet connection works perfectly (except Safari problem #A, which seem to be a Safari bug) and DNS is OK.

thx

I'm not trying to change events, but some of what you're saying doesn't match what a router does, and some doesn't match what a cable modem does.

For example, you say in post #10:
That indicates that you're connecting to a router, since self assigned addresses don't begin with 192. Those addresses are for private networks and routers perform NAT, or Network Address Translation, to allow communication between the internet and the private network.

And in post #11, you say:
That indicates your connected to a cable modem with no router, since you apparently get a new address that does not begin with 192, and you can browse the web. ——Is this correct? Do you get an address that doesn't begin with 192 on the Mac?

I've read more of the user manual for your modem, and I'm fairly sure at this point that it is not acting as a router.

If that's correct, then you're getting the 192 address (I know: post #10) from the cable company when you first connect until the DHCP server assigns a 'real' ip address. This is normal for a cable modem. Then for some reason, you lose that address temporarily and the cable company assigns another 192 address to you, but you don't get another 'real' address until you ask for one by click the Renew DHCP Lease button in Network Preferences.

At this point, assuming post #10 is incorrect, it seems likely that whatever glitch is causing the temporary loss in signal between the cable modem and the cable company is causing both the loss of the ip address and the lack of a new one being established.

If post #10 is correct, then there's something wrong with the cable modem itself. It shouldn't be providing any IP address, but instead relaying one from the cable company's servers. I'm leaning more and more towards thinking that this is the case, especially since you mentioned in your last post that your router started to fail. I'm thinking that maybe the router wasn't failing, but the cable modem was, and it was making the router look like the culprit.

well there are tons of problems with ISPs and modems. Your ISP could have done some updates which would require that your modem be updated with the newest firmware to make it more compatible. Your filter on your coax cable line could have gone bad and you can have loss of connection that way (happened to me last winter, cable guy had to come out and replace the filters), your modem could just be going bad.

What other computers do you have access to? Does the problem reproduce with them as well?

Do you have access to any kind of router? Is it in your budget to go buy one?

thanks, cwtnospam.

No. The 192 address the Mac gets comes from the cable modem. See previous posts.


No. The 192 comes from the cable modem. See previous posts.


Not exactly. The Mac eventually gets the 'real' address, after a long time. It should be available almost instantly, but takes several minutes, unless manually renewing the DHCP lease.


No. post #10 is CORRECT. With all due respect, this is a good example where you are misunderstanding the information here.


AFAIK, there is no flaw in the cable modem operation.

The problem seems to be Mac-related, imho, and the ISP confirmed that the problem is symptomatic of a Mac-related problem.

The Mac should seek a means of getting internet access when it is needed, AFAIK/IMHO.

The cable modem cannot affect or control the Mac ip address (unless the Mac requests it), AFAIK/IMHO.

As shown by manually renewing DHCP lease, the cable modem seems to respond correctly to the Mac.

The Mac should not be getting "stuck" on 192 or take a long time to resume internet access when the cable modem has a good internet connection, imho... see previous posts for more detail.


whew, finally we are discussing the actual problem which prompted this thread!



No. The router problem was not related to anything in this thread.

Here is a question for everyone:

What happens on your Mac when you lose your internet access? or your network/router connection?

Does your Mac resume internet access quickly when internet access is restored, or does it take a long time before it is back online?

I hope it doesn't confuse things, but I am trying to understand what should be expected.

This is tiring, but I'll try one last time.

Did a level 2 tech tell you so? The first person that answered the phone is just reading from a script. If they can't solve the problem, you can't take their word for it that it isn't their equipment.

Not true. When the Mac has an address it believes is valid, and 192.xxx.xxx.xxx is valid as far as the Mac is concerned, then it will not and should not request another one. The reason it changes later on is that a new one has been sent to it, not that it suddenly saw that address as bad and requested a new one.

Not true. The modem's job is to relay information from the ISP's equipment. If it is faulty, it can adversely affect any bit of information passed through it, including the Mac's ip address, as can the the cable in between.

True, but that doesn't mean that it responds correctly to all other signals, including those from the DHCP server, nor does it mean that it correctly sends every request to the DHCP server.

If you want to go on blaming the Mac, that's fine with me, but it won't get you anywhere. I've told you it's likely the cable modem or possibly the cable. JDV told you, both in post #18 and #23 that it's likely to be your cable modem or cable, and tlarkin has told you in post #44 that your modem could need an update, you could have a bad filter or your modem could be going bad.

I hope you get it fixed, but I give up at this point.

Thank you, cwtnospam, now it seems we are making some progress, but I am still having a lot of difficulty understanding some of the mechanisms here.

Yes. Of course I would not accept information blindly from an ISP rep unless I was convinced it was accurate. We discussed in detail the workings of the ISP's internet service, my observations and problems, and possible diagnosis. A cable modem problem was not ruled out completely, but could not be pinpointed to be the source of problems, either.

If the cable modem is the culprit, it is limited to only one very small specific problem, and thus I cannot say it is failing at all. I will add detail about this below.


OK, I understand that, but do not understand why the Mac will not seek to acquire internet access when it does not have it.

In my case, the Mac must have a remote ip address in order to have internet access. Can I configure the Mac to always look for this? I tempted to experiment with setting the ip address manually so it is always there, but this has two problems- 1.) if internet access is not there, it does not help anything, 2.) the address from ISP is not static and may be subject to change.



OK. But what happens in this scenario- an unconnected Mac is plugged into an ethernet network. The Mac has no ip address originally, and then gets one from the network device. Does the Mac see the physical connection and request an ip address, does the ethernet network device see the Mac and issue an ip address?

My guess is the Mac must request an ip address- but, I don't know for certain, thanks again for your patience helping me out here.

I am having trouble understanding why a network device would alter a computer's ip address without being requested to do so by the computer.


It appears that it is working correctly in this regard. What do you suggest to look for to determine if there is a problem?


It appears that it is working correctly in this regard. What do you suggest to look for to determine if there is a problem?


Here is the only problem I can isolate to the cable modem, and I am not sure it is a cable modem problem:

1. Lose internet connection.
2. Mac retains good ip address, but has no internet access.
3. Restore internet connection.
4. Power-cycling the modem. [Mac usually has lost ip address at this time, or during power-cycling.]
5. Modem assigns 192 address to Mac.
6. 192 gets stuck on Mac, instead of getting good ip address.
7. After a few minutes, Mac gets good ip address.

Workarounds:
- unplug and re-plug Mac ethernet cable. good ip address is assigned instantly.
- manually renew DCHP lease. good ip address is assigned instantly.


Note that this is Problem #2 that I listed. Problem #1, #A, #B are separate problems and also still remain unsolved and unexplained.


cwtnospam, you have helped me very much to understand that the delay in Problem #2 occurs in a certain type of situation, and it is only temporary (a few minutes).

But does the delay indicate a problem exists, or is it how things are supposed to work?

IMHO, the delay should not occur, but I do not know for certain, thus I started this thread to hope to understand and preferably to find a solution.

does the IP change, or is it the same IP over and over again it keeps getting assigned?

The good ip address stays the same.

The 192 address seems to be the same all the time (I haven't always looked closely).

it kind of sounds like your modem from what you described. Also, just so you know your ISP, no matter what level of tech (could be a level 50 wizard tech) will almost always blame your equipment first.

Maybe if I explain my setup, it will help you to understand yours.

I have a cable modem and two routers. The first router is a Lingo VOIP router. As a router, it is terrible, but it needs to be the first thing connected to the cable modem in order for my phone to work. This is important because of what happens on the rare occasions we lose our cable (both TV and computer, nobody knows why) for up to ten minutes.

When this happens, the Lingo router very often will not connect back to the ISP when cable returns. To re-establish access, I need to connect the computer directly to the modem, wait for it to get an address, and then switch the ethernet cables back to their normal setup. When I do this, the Mac first gets an address that begins with 192 from the cable modem (more precisely, from the cable company) that lasts for at most a couple of seconds before being replaced with a routable internet address. That's when I switch cables back and the Lingo router can connect.

If your cable company's setup is anything like mine, then you're getting that initial local address but not receiving the routable address until much later. It's likely that the DHCP server sent it to you, but you didn't receive it because of a bad cable or modem, and then at a later time, the cable company's system sees that you're still on the local address, so it sends it again. This process could repeat itself many times before an address finally gets through, resulting in considerable delays.

Note that the Mac is quite happy to go along using the 192 address forever, and will not request another address as long as it has this one. In fact, my Mac's address right now is: 192.168.0.100 because it is connected to a router which does Network Address Translation (NAT) so that my Mac can communicate with the internet.

As I see it, your biggest problem at this point is going to be convincing the cable company that something like this is going on and they need to send somebody out to fix it. As Tlarkin pointed out, they're inclined to blame your system first. They get paid to close tickets quickly, and blaming your computer is the fastest way to do that.

Could anyone please answer the question above for me?

It will help me understand what I should expect to see happen between the Mac and the cable modem and greatly help me to isolate the problem further.

Perhaps, but I what I observe does not match your suggestion that the cable company sends information to the modem in response to the status of the Mac.

1. If get delay after power-cycling modem, the delay seems to be the same amount of time (several minutes) consistently. That rules out a problem where you suggest the ip address has to be re-sent because it has not been received properly.

2. If Mac is unattended and internet connection has been lost, but internet connection to modem is restored, the Mac almost never gets back online unattended. (I will call this "Problem #4"). That suggests that even if ISP sees the Mac is only locally connected, the ISP does not do anything in response. That also rules out a problem where you suggest the ip address has to be re-sent because it has not been received properly. On the contrary, it appears like it is never sent, thus the Mac remains offfline.

IMHO there is no problem between the modem and ISP.

I agree there is some possible problem between the Mac and the modem.

But I am not convinced the modem has such a specific failure as to only have the problems I am seeing.

Perhaps this link may help: http://homepage.ntlworld.com/robin.d...hcp.html#lease

It is essentially a two-way process.

Joe VanZandt

Here is some additional info:

cwtnospam- as I said, the modem will give the Mac a 192 address, even if the internet is physically disconnected. So, in this case, the ISP is very definitely NOT sending the local ip address to my Mac.

However, you also mention getting 192 address from ISP before getting "good" ip address from ISP. I see the same thing as you describe when getting the good ip address. It is always preceded by the Mac completely losing ip address. ie.,"stuck" 192 => few minutes delay => no ip address => 192 => good ip address). I cannot determine if the 192 address at this point is from the ISP or modem.

Here is the revised sequence of events:

1. Lose internet connection.
2. Mac retains good ip address, but has no internet access.
3. Restore internet connection.
4. Power-cycling the modem. [Mac usually has lost ip address at this time, or during power-cycling.]
5. Modem assigns 192 address to Mac.
6. 192 gets stuck on Mac, instead of getting good ip address.
7. After a few minutes, Mac gets good ip address. Here is the more detailed sequence of getting a good ip address at this point in time:
7a. Mac loses ip address.
7b. Mac gets 192 address. [I cannot determine if this 192 is from modem or from ISP. It is same address as when internet is physically disconnected.]
7c. Mac gets good ip address.

7a-7c happen within a few seconds.

Let me repeat: 192.168.x.x addresses are assigned by your local router (modem) because it is a non-routable IP address...it won't go past a router. So it is NOT being assigned by your ISP. Your router (modem) is assigned an valid, routable IP by your ISP through DHCP (those often remain constant for long periods, but it isn't the same as PAYING for a static IP--you aren't guaranteed it won't change). The router uses Network Address Translation (NAT) to provide your machine (with its non-routable IP of 192.168.x.x) with access to the outside world via the IP address assigned to your modem. Everyone who uses a typical router has an 192.168.x.x IP, but this provides no conflict because the outside world cannot SEE that address directly. It is internal to the network created by your router. If you use a simpler modem with NO routing abilities, the IP you would see would be the actual IP assigned by the ISP to your modem. This is generally considered risky because that opens your machine up DIRECTLY to the outside world, with all the attendant perils.

Joe VanZandt

Thanks for confirming, that was my understanding also, and thus I have been questioning some of the conflicting information in this thread.

I suppose it's possible that my cable modem and yours both supply a local (192.xxx.xxx.xxx) address (I'll test this later, when I'm sure I won't need internet access for a while) until they receive a valid ip address from the ISP, but it really doesn't change anything. Either way, your scenario fits:

1. Lose internet connection -- the modem is faulty and doesn't register this fact.

2. Mac retains good address because the modem hasn't recognized that it lost the connection, so it continues to signal a good connection to the Mac.

3. internet connection restored -- modem light says good, but this isn't trustworthy. All it means is that it thinks that it's got a good connection to the central office, not to the DHCP server or the rest of the internet. Even if it does have those, it's problem might be on the ethernet side. I tend to doubt this because it's more likely to receive a surge on the cable side.

4. Power-cycling the modem. Mac lost ip address because the modem finally recognized that it didn't have a valid connection and told the Mac.

5. Modem assigns 192 address to Mac.

6. 192 gets stuck on Mac, instead of getting good ip address because the modem didn't get one from DHCP. Why? Bad modem, bad cable (either coax or ethernet), other signal leak in house or on the street.

7. After a few minutes, Mac gets good ip address. Here is the more detailed sequence of getting a good ip address at this point in time:
7a. Mac loses ip address. -- Modem recognizes signal loss, revokes Mac's ip address.
7b. Mac gets 192 address. [I cannot determine if this 192 is from modem or from ISP. It is same address as when internet is physically disconnected.] Either way, same problem: Modem did not get a valid ip to pass on to the Mac.
7c. Mac gets good ip address. After who knows how many attempts, the modem gets an address from the DHCP server and passes it on to the Mac.

Don't try to make too much sense of the problem. Remember that it's possible for one tiny part of the cable modem to be bad, or one tiny, sporadic short to exist in the cabling that could be causing errors all the time without dramatically affecting your service accept for when it occurs at just the right moment. You could be experiencing slightly slower speeds (ie, 1.4999 mbps instead of 1.5 mbps) because of the same problem, but when it affects your ip address, it's all or nothing so the problem seems much larger. Then you have to go through the whole cycle, which may not error correct as well as when transmitting normal data.

There is a lot of misinformation posted by a few people in this thread.

The description I have given above is accurate.

Thank you to individuals who identified correctly what was happening.

To recap:
1. internet connection is lost.
2. modem recognizes connection is lost.
3. mac loses internet connection.
4. mac connects to modem via local address.
5. mac fails to renew DHCP from provider, because local address is considered valid.
6. current workaround- manually renew DHCP via System Preferences:Network.


At this point, I would welcome some useful suggestions for solving the problem, rather than guesswork and speculation.

A useful solution involves Mac restoring valid internet connection without any user intervention, and doing so very quickly.


Thanks in advance.