I am posting this question as a last resort. I have been troubleshooting a connectivity issue with my internet for a few months now. Since April, I have been experiencing 1-3 second loss of internet every 30 minutes to 2 hours. The time period between the losses is entirely random and unpredictable.

This problem happens across multiple different programs and activities. If I am downloading a file, the download will fail (Chrome and Firefox). If I am using a VPN or connecting somewhere via SSH or Remote Desktop, the connection will drop. I often observe the connection dropping over voice chat (Mumble), which has both UDP and TCP options. If I am running UDP mode, voices will cut out and will never come back, but I will not disconnect from the server. If I force TCP mode, I will disconnect from the server and automatically rejoin a few seconds later. If I run a continuous ping test, the issue will present as 1-3 "Request timed out." lines amidst a sea of normal pings to Google.com.

I have fiber-to-the-doorstep municipal internet that connects via a box on the outside of my home that serves as "modem" that I have no physical or software access to. I have been working with them to troubleshoot the problem, to no avail.

I have tried all of the above with the problem still occurring:

• A new router (Cisco Linksys E2500 running DD-WRT, upgraded from Linksys WRT54GL)
• A new network interface card
• Multiple computers (two desktops and a laptop, desktops Windows 7 and laptop Ubuntu Trusty Tahr)
• Connecting directly to the connection from the wall, bypassing the router
• A new Cat5 cable to my computer

My ISP has tried:

• Switching the port on the box on the exterior of my home (which acts as the modem)
• Switching out the board inside the box on the exterior of my home
• Switching the cable that runs from the box into the house
• "Upgrading" me to a higher speed/tier of service by switching my subnet temporarily, which did not fix the problem
• Presumably internal diagnostics/port checking on the other end of the connection (they find no significant packet loss)

Their next step is adding some sort of new box on the exterior of my house that will allow the engineer working my case to see light levels from the fiber in real time. I think I have done everything eliminate the possibility that the problem is in my hardware. What else could I try and/or what could be causing a problem like this?

Update: my previous statement that these cutouts are random appears to have been false. The issue is occurring at the 52 minute mark when my DHCP lease drops and my IP is renewed. While my IP address is not changing, my devices seem to be failing their half-remaining-time lease renewal. The ISP claims a minimum lease time of 60 minutes is set, but my lease remains 51-52 minutes. I am assuming the drops are because my lease is dropping temporarily and requesting a new one. What could be causing my half-remaining-time check-in to fail every time? I expect it is on the ISP side, since it happens with all of my devices and regardless of my router, but I don't know enough about ISP infrastructure to hazard a guess or do any tests.

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1 Answer

It sounds to me like the IP address of something is changing - My next step would be to undertake some monitoring - both of the IP address of the router and the IP address on your computer.

You might want to eliminate the possible issue of DHCP on your computer by providing a static IP address - but I'd suspect the issue is at the ISP side, unless you have lots and lots of devices oveflowing your address space, which seems to me to be less likely.

A change of IP address could explain the TCP/UDP issues symptoms.

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