Network goes offline

[Deth]

Hi.
I've been running into a really weird network issues lately.
I had a mac mini 2012, i normally connect to the internet with a straight line to the cable-modem (no routers or split things) but once in a while the connection just goes offline (network panel report cable is unplug) and the modem report that there is no computer connected to it, if i unplug the cable on the mac mini and plug it on the macbook it gets the connection immediately with no issue.

Thinking that it may be a wire issues i change the cable and still happens now and then...

when the mac mini get into that "state" i can't make any connection by the enthernet port, not even connecting one mac to the other.

Restarting it doesn't fix the problem, the only way to fix it is to shut it down for a couple of hours and then turn it on again (just a minutes doesn't seems to fix it don't know why)

Does anyone have an idea of whats going on?
Thanks

 

[illusionx]

Network goes offline

Question, why aren't you using a router? Seems that's what you should do rather than unplugging your computer all the time. And by plugging it directly, you are exposing your computer directly to the Internet.

Anyways, when this happens, does sys pref show the network is disconnected or it shows no IP?

Cable modems have a limit how many MAC address can access the network(Internet) at any given time. That's the DHCP lease. When you get into that "state", it is likely you wait to wait till the lease expires before you ca get it to work again.
Happened to me when I was trying to configure 10 routers in a day... Hit a wall after 4 and i couldn't get on the internet until all the DHCP leases expired.

 

[Deth]

Lost me with the router stuff, if you got only one desktop computer and the cable modem is right there why you need a router? (isn't the cable modem something like a router anyway? ..sorry maybe im mixing the terms) the mac mini normally uses the wifi to share connection to anything else that need internet.

Anyway, nope, the system preferences says that the cable is not plugged in, even if i connect it to the macbook with the enthernet cable

Yes, I tried to get into advanced and click on the "renew DHCP lease" but it does nothing.
Ok the part that i have to wait until the lease expire kinda makes sense but the only thing connected to the modem is this computer

Don't know if helps, the modem is a Motorola Surfboard SB5101N

 

[illusionx]

Network goes offline

Try rebooting the modem see if it fixes the issue when that happens. Just unplug the power, wait a few seconds and plug it back.

I just advise against being directly connected to the Internet unless you have a good software firewall. Anyways whatever works for you. But try to unplug the modem when that happens.

 

[Fishrrman]

OP asks above:
[[ Lost me with the router stuff, if you got only one desktop computer and the cable modem is right there why you need a router? ]]

The router would offer something called NAT (network address translation) that acts like a "hardware firewall" to provide a level of "insulation" against the net.
As illusionx mentioned above, it's not a good practice to have any computer plugged "directly into the internet" without something "in between" to offer some protection.

Having a router (even if it's only a "wired router" without any wifi capabilities) will also make it easy to add additional equipment if you need to do so.

If you don't need wifi, you could probably pick up an older wired router for next-to-nothing via ebay, etc. I used to use an old Belkin router that was easy enough to set up and worked without problems.

 

[840quadra]

It sounds like there is an issue with the Mac Mini's NIC maintaining a reliable link with your Modem.

Are there any differences in settings on your Macbook, as compared to your Mac Mini? You may need to click advanced to see if there is a hard set speed / duplex. Also, Your ISP may be able to log into your modem, and see if it is reporting errors, and give you an idea if your issue is with your Mini, or the Modem itself.

Since the connection issue appears to also limit you connecting your Mini with other devices via Ethernet, it may be that you have a hardware issue with that ethernet port itself. it may take digging deeper into your log files to see if the system is showing errors, however reading through those can be confusing and frustrating by itself.

With regards to your home network Security, since your Mini appears to be the only device attached to the internet you can Turn on MacOS firewall, which will add the same level of security as many basic router's firewall function, and depending on the settings you enable, can actually be more secure.

The additional settings you can look into would be to enable Stealth mode, and if you only need to access the internet / websites, Block all incoming connections.

These settings will still allow you to access the internet, and you can add applications (rules) to allow additional applications inbound and outbound internet access as needed.

 

[Deth]

Ok, thanks guys... it seems that my security is really bad LOL
I never really thought too much on that to be honest...
Well, i do use Little snitch to watch on the incoming connections and other stuff...

Anyway, the hardware settings may be the answer, the ISP ask me to put specific settings manually in order to connect to the internet, the macbook is in automatic, but still one that i got in that "state" even changing the settings to automatic will not make it work unless i turn the computer off and wait a couple of hours

I checked the modem log, see a lot of things that looks like an error but never knew what they mean.

Resetting the modem doesn't work, and as i said once in got in that state i can't even connect to the macbook in a simple LAN connection, so i think the issues are on the mac mini and not in the modem

I'll take a look on the console and see what happen around the moment of the failure

 

[illusionx]

If the issue was the mini, you really shouldn't have the issue with the macbook.

 

[Deth]

If the issue was the mini, you really shouldn't have the issue with the macbook.

Well it doesn't...

The mini is the one that goes offline and cannot connect to anything by the enthernet port, not even the macbook.
When that error happens and the mini got offline, if i connect the macbook to the modem it works perfectly, so it is the mini the one with the issues since the modem comes back to life immediately after i plug it to the macbook or other device.

 

[Fishrrman]

I would still recommend that you pick up a router -- either a modern wireless-capable router or an older "wired only" router -- and install that "between" the cable modem and your Macs.

You -WANT- a hardware-based firewall between yourself and the net!

 

[adamhenry]

I would still recommend that you pick up a router -- either a modern wireless-capable router or an older "wired only" router -- and install that "between" the cable modem and your Macs.

You -WANT- a hardware-based firewall between yourself and the net!

Gotta agree with that. When you hook a computer to the modem, it becomes a target. A router will assume the target role when it is attached and provide nice shield for the computers attached to it.