Sporadic internet connectivity issues

Installing and Using OpenWrt
21

Heh, I didn't know that. I just assumed it was the default for the devices I have used (all Arris modems), but I didn't know that it was actually part of the spec. Cool!

That said, if it turns out that the modem isn't actually using that address, I wouldn't necessarily think of the deviation as the operator's fault, but rather the manufacturer (Motorola, in this case). I guess it would depend on if this is 'configurable' by the ISP, or if it is coded into the firmware of the device by the manufacturer. However, beyond this theoretical angle, I have no actual information to contribute... :rofl:

22

In your screeshot there is a tab called "Firewall Settings", click that and assign MODEM to the wan zone.

I am not sure that this will fix your problem though, as I said it is a loooong time since I used docsis (and that was back when I had little operational knowledge about networking so what I might have done back than might have been completely superfluous).

23

see cisco's bulletin:
" Operations Alert Bulletin
Limitations on Headend IP Addresses for Set-Tops in DOCSIS Mode

Background

Engineers at Cable Television Laboratories, Inc. (CableLabs®) have reserved the 192.168.100.1 IP address for diagnostic purposes for cable modems. Because CableLabs did not specify a subnet mask, Cisco chose 255.255.255.0, the Internet standard for a Class C IP address.

If a headend server is assigned an IP address in the 192.168.100.0/24 subnet, then neither the cable modem nor the set-top itself will be able to communicate with the headend server, resulting in possible service outages. Examples of headend servers include the Digital Network Control System (DNCS), the video-on-demand (VOD) server, the Dynamic Host Configuration Protocol (DHCP) server, and the Trivial File Transfer Protocol (TFTP) server.

Recommendation

System operators must avoid assigning an IP address in the 192.168.100.0/24 subnet to any headend server. Any headend servers that currently have an IP address in the 192.168.100.0/24 subnet must be assigned a new IP address. Furthermore, no set-top or cable modem can be assigned an IP address in the 192.168.100.0/24 subnet, either.

Note: Set-tops that operate in DAVIC mode are not affected by this limitation."

This should also be in:
" Data-Over-Cable Service Interface Specifications DOCSIS 3.0

Operations Support System Interface Specification"

But I can not check since the cablelabs library is offline until next week to deal with log4j fall-out:
"The specifications library is currently unavailable due to a critical vulnerability in Log4j. The library will be patched and will be back on or before January 3, 2022. Thank you for your patience."

2 Likes
24

That's really useful info @moeller0 ! Thanks.

1 Like
25

No matter what you think about DOCSIS, cablelabs standards library is an excellent resource.

1 Like
26

More info on pings.
Once a website is inaccessible, it is for the whole network.
Below is a collection of pings for various websites and their outcome from my router.
Please note, the ones that work are solid. If it pings once, it can ping continuously indefinitely without issue.
The ones that do not work will never work until the router is rebooted, where they will work for a short time.

oot@OpenWrt:~# ping stackoverflow.com
PING stackoverflow.com (151.101.65.69): 56 data bytes
^C
--- stackoverflow.com ping statistics ---
31 packets transmitted, 0 packets received, 100% packet loss
root@OpenWrt:~# ping facebook.com
PING facebook.com (2a03:2880:f127:83:face:b00c:0:25de): 56 data bytes
64 bytes from 2a03:2880:f127:83:face:b00c:0:25de: seq=0 ttl=53 time=25.935 ms
64 bytes from 2a03:2880:f127:83:face:b00c:0:25de: seq=1 ttl=53 time=22.664 ms
^C
--- facebook.com ping statistics ---
2 packets transmitted, 2 packets received, 0% packet loss
round-trip min/avg/max = 22.664/24.299/25.935 ms
root@OpenWrt:~# ping reddit.com
PING reddit.com (151.101.193.140): 56 data bytes
^C
--- reddit.com ping statistics ---
15 packets transmitted, 0 packets received, 100% packet loss
root@OpenWrt:~# ping apple.com
PING apple.com (17.253.144.10): 56 data bytes
64 bytes from 17.253.144.10: seq=0 ttl=56 time=31.686 ms
64 bytes from 17.253.144.10: seq=1 ttl=56 time=30.365 ms
64 bytes from 17.253.144.10: seq=2 ttl=56 time=29.908 ms
^C
--- apple.com ping statistics ---
3 packets transmitted, 3 packets received, 0% packet loss
round-trip min/avg/max = 29.908/30.653/31.686 ms
root@OpenWrt:~# ping coinbase.com
PING coinbase.com (2606:4700::6812:60a): 56 data bytes
64 bytes from 2606:4700::6812:60a: seq=0 ttl=54 time=25.977 ms
64 bytes from 2606:4700::6812:60a: seq=1 ttl=54 time=24.025 ms
^C
--- coinbase.com ping statistics ---
2 packets transmitted, 2 packets received, 0% packet loss
round-trip min/avg/max = 24.025/25.001/25.977 ms
root@OpenWrt:~# ping fox.com
PING fox.com (23.11.208.173): 56 data bytes
64 bytes from 23.11.208.173: seq=0 ttl=53 time=36.401 ms
64 bytes from 23.11.208.173: seq=1 ttl=53 time=36.840 ms
^C
--- fox.com ping statistics ---
2 packets transmitted, 2 packets received, 0% packet loss
round-trip min/avg/max = 36.401/36.620/36.840 ms
root@OpenWrt:~# ping stackexchange.com
PING stackexchange.com (151.101.193.69): 56 data bytes
^C
--- stackexchange.com ping statistics ---
18 packets transmitted, 0 packets received, 100% packet loss
root@OpenWrt:~# ping youtube.com
PING youtube.com (2607:f8b0:4009:818::200e): 56 data bytes
64 bytes from 2607:f8b0:4009:818::200e: seq=0 ttl=116 time=22.857 ms
64 bytes from 2607:f8b0:4009:818::200e: seq=1 ttl=116 time=23.410 ms
^C
--- youtube.com ping statistics ---
2 packets transmitted, 2 packets received, 0% packet loss
round-trip min/avg/max = 22.857/23.133/23.410 ms
root@OpenWrt:~# ping funimation.com
PING funimation.com (45.60.109.224): 56 data bytes
^C
--- funimation.com ping statistics ---
20 packets transmitted, 0 packets received, 100% packet loss
root@OpenWrt:~#

In summary:
stackoverflow.com - Nope
facebook.com - Good
Reddit.com - Nope
Apple.com - Good
coinbae.com - Good
Fox.com - Good
Stackexchange.com - Nope
Youtube.com - Good
Funimation.com - Nope

A Traceroute of a broken website returns no results for the first 3 hops. After that, some pop up sparingly 4-7. Then hop 8 and onward is all broken again.

The only clue I've gathered here is
Nslookup only returns both iPV4 and IPV6 for those domains that worked.
Nslookup only returns IP4V on the domains that did not work.
But, as you can see pings on some of those that did work, some of them are working with ipv4 addresses.

Example:

root@OpenWrt:~# nslookup youtube.com
Server:         127.0.0.1
Address:        127.0.0.1#53

Non-authoritative answer:
Name:   youtube.com
Address: 142.250.191.142
Name:   youtube.com
Address: 2607:f8b0:4009:808::200e

root@OpenWrt:~# nslookup funimation.com
Server:         127.0.0.1
Address:        127.0.0.1#53

Non-authoritative answer:
Name:   funimation.com
Address: 45.60.109.224
Name:   funimation.com
Address: 45.60.73.224

Does anyone have an idea of what this may mean?

27

Try cloning the MAC address of the DOCSIS modem to the router WAN interface.

Then, SSH in to the router and run ifup wan from the CLI.

Retest.

Screenshot 2021-12-30 235613
Screenshot 2021-12-30 235613697×587 36.7 KB

28

I just preformed these steps, and things seem to be working. I can ping all of those sites that didn't work before.
It's usually a 6 hour window before they stop working again after a restart, so I'll report here tonight if they continue working.
Could you explain what cloning that mac on the interface does?
Thank you.

29

Some ISPs lock down the availability of the Internet circuit by MAC address...so, only their provided devices (i.e. the DOCSIS modem) can connect.

By doing "MAC spoofing", the router is now recognized as a "legitimate" ISP device.

30

I was having a similar problem and found my network cable was loose going from my OpenWrt device to my modem. If you haven't already check your cables and possibly try a fresh or proven cable.

[Edit to add: Also, someone else had to have their service provider come out and check the line from their modem to the street where an issue was found. This was more severe than sporadic connection issues.]

31

May I ask if your issue is fixed?
I'm experiencing similar issues. But not exacly the same.
On a cable modem too..

Sometimes Youtube page is very slow to load, Facebook comments under a post are not loading, etc. But if I put my phone on LTE, it loads very fast.

It's not a internet speed issue as speedtests are OK. So i'm thinking of dns resolution or something like that, or maybe it's the same issue as you!

Thanks