Dropping network connection once/twice per day on Debian 7.5 Realtek RTL8111/8168B
 

I was having a connectivity problem where the network connection just drops about once or twice a day. I yesterday I ran update and upgrade with 0 errors. However, I am still having the same network connectivity problem. I opened up Network Connections from the Applications | System Tools menu, and believe it or not, there is no connection under Wired Connections, but I am still able to internet, although with stated hiccups. Where can I begin to troubleshoot this issue?

Much thanks in advance for your help.

What's the output of ifconfig? All fields except TX, RX, and txquelen should be 0.

To me it sounds like something is wrong with the switch or router you are connected to.

Are there any Ethernet device errors in the output if you type
dmesg
?

OP Reply #1
 

I am perplexed by the output of:

A screenshot below shows proof.

As to the dmesg command, I ran:

to send entire output of dmesg command to a simple text file, which I opened in gedit. Then I copied contents of what is shown to the box below:

See following post for continuation.

OP Reply #1 (continued)
 

Continued.

Please see first TXT file attachment below. Forum was pushing me back due to misinterpreted tags.

I couldn't see any errors, but then again, I am not an expert--I'm more like an advanced novice/lower-intermediate. Maybe there is some error(s) that you can see that I couldn't pick up.

At any rate, my system has been up continuously for two days now, and I haven't experienced a network drop since I rebooted. This is a good sign. Although, I don't know why ifconfig is not available. I tried to see if I can install it from Synaptic, but you see from the attachment on immediately previous post that it is not available, and I know that I have all the necessary sources in sources.list. (Please see second attachment to this post).

Would you be able to help me make ifconfig available/installed on my machine? I tried to apt-get/install it, but it could not find ifconfig.

BTW, both PNG attachments are on Part 1 of this reply.

Thanks in advance for your help.

It turns out ifconfig is installed, it is just not in my PATH. I will fix that later, and continue troubleshooting with results of ifconfig later on today. (The system dropped my network connection again earlier this morning).

If you don't have it in the path you can call it with the path, like:

/sbin/ifconfig

How long has the machine been up? If you give the output of dmesg after it's dropped it may indicate what the drop is caused by. Also you could issue a sudo command to show the last 20 lines from the logfile. It's important to let the issue occur at least once before doing this.

sudo tail -n 20 /var/log/syslog

ifconfig must be run as root, in most distros.

Alright, back to this question that I have yet to answer, but is probably pertinent to our troubleshooting efforts.

So, that corresponds appropriately with your earlier statement that:

...

It does not look like the Linux machine is dropping the network connection. I suspect that the device that provides the Linux machine the network is causing the drops.

The dmesg command would show link drops:

ADDRCONF(NETDEV_UP): eth0: link is not ready
e1000e: eth0 NIC Link is Up 1000 Mbps Full Duplex, Flow Control: RX/TX
ADDRCONF(NETDEV_CHANGE): eth0: link becomes ready
ADDRCONF(NETDEV_UP): eth1: link is not ready
e1000: eth1 NIC Link is Up 1000 Mbps Full Duplex, Flow Control: RX/TX
ADDRCONF(NETDEV_CHANGE): eth1: link becomes ready

You would possibly have errors or frame drops. None of these are present so I'd check the cable wire is tight on the router with a wrench.

Had this happen years ago, the cable tech took out a 7/16 out and tightened the F fitting to solve the issue.

...
Alright, got to this step so far. I will just give my system time, and when/if the connection drops, I will carry out your instructions for dmesg, and tail of syslog. In the meantime, I will fish around to get ifconfig in my path, in the order I prefer for it to be in.

Thank you in advance for your help.

Will do. Will tighten fitting and give it time--max until Monday morning. If you haven't heard from me by then, will close thread as [SOLVED].

Thank you.

As suggested, I am attaching in a file the last several lines of my syslog, from a network disconnection this morning. You asked for 20, but I am giving 100, for good measure. Would you please see attached file, review it, and let me know what you think?

Thank you.

Is the cable too long or it has not been follow EIA/TIA 568A & 568B Standard? Non standard or bad cable can cause a lot of trouble.
Realtek LAN chipset is cheap one make for desktop so I assume this using a Desktop motherboard. Defected LAN chipset also can cause this issue. For server purpose, Intel or Broadcom provide chipset with higher performance, feature rich and stability.
What message has been written to /var/log/messages at the time you lost your connection (like kentyler's suggestion)?

I have used the same cable, the same modem, and the same everything (except for software updates) for at least two years now, and have had no trouble up until just recently. Why would non-standard cable all of a sudden conflict with my attempts at keeping a stable network connection? But, assuming your question is appropriate, how would I determine if it is standard?