Score:2

Ubuntu

Ubuntu 18.04. Sudden DSL connection degrading - on and off - inconsistent slow connection to websites

Imparo Ubuntu

2/10/23, 4:27 AM

I have been using my rig with no problems for 2 years. Nothing change in the last days in terms of ISP etc... Suddenly I am experiencing troubles with my internet connection. Often I go to my favorite sites like Amazon or Wal Mart for online shopping and the page does not resolve DNS issues. etc... Youtube videos take forever to load. Or have a black screen and then suddenly starts.

Basically what used to be a solid and consistent internet connection is close to almost useless.

$ ls -al /var/crash
total 94492
drwxrwsrwt  2 root     whoopsie     4096 Oct  9 20:58 .
drwxr-xr-x 15 root     root         4096 Dec 16  2020 ..
-rw-r-----  1 user  whoopsie 93889664 Oct  9 20:50 _opt_google_chrome_chrome.1000.crash
-rw-r--r--  1 user  whoopsie        0 Oct  9 20:50 _opt_google_chrome_chrome.1000.upload
-rw-------  1 whoopsie whoopsie        0 Oct  9 20:58 _opt_google_chrome_chrome.1000.uploaded
-rw-r-----  1 user  whoopsie  2852391 Oct  2 22:55 _usr_bin_file-roller.1000.crash
-rw-r--r--  1 user  whoopsie        0 Oct  2 22:55 _usr_bin_file-roller.1000.upload
-rw-------  1 whoopsie whoopsie        0 Oct  3 10:42 _usr_bin_file-roller.1000.uploaded


$ free -h
              total        used        free      shared  buff/cache   available
Mem:           7.7G        1.4G        4.2G        134M        2.2G        5.9G
Swap:          4.0G          0B        4.0G

Any help is greatly appreciated as I remain a very basic user of linux.

PS: BTW other computers and smart televisions and phones at my house are not experiencing any internet connection issues at all either Wi_fi or DSL.

PS: When I went to restart I now see a black screen that says "Failed to start Network manager".

$ tracepath www.amazon.com 1?: [LOCALHOST] pmtu 1500 1: modem.Home 4.305ms 1: no reply 2: modem.Home 72.534ms pmtu 1492 2: tukw-dsl-gw68.tukw.qwest.net 53.848ms 3: tukw-agw1.inet.qwest.net 24.760ms 4: 99.82.182.74 24.713ms asymm 5 5: 52.95.55.223 25.652ms asymm 8 6: 150.222.237.55 24.320ms asymm

    $ sudo lshw -C network
      *-network                 
           description: Ethernet interface
           product: Ethernet Connection I217-LM
           vendor: Intel Corporation
           physical id: 19
           bus info: pci@0000:00:19.0
           logical name: eno1
           version: 04
           serial: c8:1f:66:ac:5b:36
           size: 1Gbit/s
           capacity: 1Gbit/s
           width: 32 bits
           clock: 33MHz
           capabilities: pm msi bus_master cap_list ethernet physical tp 10bt 10bt-fd 100bt 100bt-fd 1000bt-fd autonegotiation
           configuration: autonegotiation=on broadcast=yes driver=e1000e driverversion=3.2.6-k duplex=full firmware=0.13-4 ip=192.168.0.14 latency=0 link=yes multicast=yes port=twisted pair speed=1Gbit/s
           resources: irq:31 memory:f7d00000-f7d1ffff memory:f7d3d000-f7d3dfff ioport:f080(size=32)
      *-network DISABLED
           description: Wireless interface
           physical id: 1
           bus info: usb@3:1
           logical name: wlx1cbdb9dfc01d
           serial: 1c:bd:b9:df:c0:1d
           capabilities: ethernet physical wireless
           configuration: broadcast=yes driver=r8712u multicast=yes wireless=unassociated

$  cat /etc/network/interfaces
# interfaces(5) file used by ifup(8) and ifdown(8)
auto lo
iface lo inet loopback
mtu 1450

$ cat /etc/netplan/*.yaml
# Let NetworkManager manage all devices on this system
network:
  version: 2
  renderer: NetworkManager

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networking

internet

dns

dsl

connection

guiverc

2/10/23, 4:44 AM

Providing your OS & release details are a start. Have you confirmed you don't have a hardware issue? (on the router etc). *This detail should be in your question; not just title as not all browser setups show the title when viewing the actual question*

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Imparo Ubuntu

2/10/23, 4:46 AM

@guiverc Ubuntu 18.04. Router works with other laptops.

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pasman pasmański

2/10/23, 5:27 AM

Prepare thumb drive with fresh Ubuntu installation image and start your laptop from it (in "Try Ubuntu" mode). Browse some web pages. Is visible any difference ?

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heynnema

2/10/23, 1:24 PM

Install `iputils-tracepath` and then do `tracepath www.amazon.com`. Tell me the MTU setting in your Wired Connection profile. Show me `sudo lshw -C network` and `cat /etc/network/interfaces` and `cat /etc/netplan/*.yaml`.

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Imparo Ubuntu

2/10/23, 4:41 PM

@heynnema '~$ tracepath www.amazon.com 1?: [LOCALHOST] pmtu 1500 1: modem.Home 4.305ms 1: no reply 2: modem.Home 72.534ms pmtu 1492 2: tukw-dsl-gw68.tukw.qwest.net 53.848ms 3: tukw-agw1.inet.qwest.net 24.760ms 4: 99.82.182.74 24.713ms asymm 5 5: 52.95.55.223 25.652ms asymm 8 6: 150.222.237.55 24.320ms asymm`

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Imparo Ubuntu

2/10/23, 4:51 PM

@heynnema I put the answers to the other commands you kindly shared in the body of the original Question as output is too long.

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Imparo Ubuntu

2/10/23, 5:15 PM

@heynnema I put a screenshot of the internet speed test. It says connection is fast. But the reality is it has visibly degraded and I keep get the site can't be reach DNS page every so often. My machine is just not what it was a few days ago. Mystified :-(

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Imparo Ubuntu

2/10/23, 7:00 PM

@heynnema. I made the changes. A little better but not quite back where I used to be. I really appreciate your knowledge and help. I really don't know what happened. Should I update to Ubuntu 20.04 from 18.04 next time I get prompted? Spent so many hours on this... it feels like a reinstall at this point. Do you have any more aces up your sleeve :-)?

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heynnema

2/10/23, 7:05 PM

Sure, reinstall 18.04 or upgrade to 20.04. Make sure your `Software Updater` is current, and you'll get the prompt to upgrade. What is the WAN MTU set to in your router?

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Imparo Ubuntu

2/10/23, 8:19 PM

@heynnema I took a screenshot of where the WAN MTU should be but I could not find it. I will keep digging.

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heynnema

2/10/23, 8:20 PM

Those settings are fine. It's properly detected PPPoE.

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Imparo Ubuntu

2/10/23, 9:26 PM

@heynnema What is the command line to check the WAN MTU? I could not find it logged as Admin in the Century Link Configuration

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Imparo Ubuntu

2/10/23, 9:29 PM

@heynnema `$ ping -s $((1492 - 28)) -D 8.8.8.8 -c 1 PING 8.8.8.8 (8.8.8.8) 1464(1492) bytes of data. [1633901313.181328] 76 bytes from 8.8.8.8: icmp_seq=1 ttl=117 (truncated) --- 8.8.8.8 ping statistics --- 1 packets transmitted, 1 received, 0% packet loss, time 0ms rtt min/avg/max/mdev = 270.618/270.618/270.618/0.000 ms`

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Imparo Ubuntu

2/10/23, 9:29 PM

@heynnema is this what you had in mind when referring to WAN MTU? Thanks as always.

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heynnema

2/10/23, 11:22 PM

The MTU can be seen in the `tracepath` command, as pmtu. Note in your example, it was 1500 at your computer, and 1492 after the modem. Question... in your ping command, where did the **$((1492 - 28))** come from? I ask because the ping was truncated.

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heynnema

2/10/23, 11:31 PM

See Update #1 in my answer.

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Score:2

Ubuntu

heynnema

2/10/23, 6:31 PM

Change /etc/network/interfaces...

From:

# interfaces(5) file used by ifup(8) and ifdown(8)
auto lo
iface lo inet loopback
mtu 1450

To this:

# interfaces(5) file used by ifup(8) and ifdown(8)
auto lo
iface lo inet loopback

Change your Wired Connection profile...

Because of DSL, change MTU from automatic, 1500, or whatever it is, to 1492.

Reboot and retest.

Update #1:

Note: I placed this here just in case it's required to manually determine that 1492 is the correct setting. First reset MTU to 1500, reboot, and then follow the instructions.

Your problem is with the MTU setting for your DSL connection.

There's a MTU setting in Ubuntu's network configuration, and a WAN MTU setting in your router.

For DSL, a common MTU setting is 1492. Just go ahead and try this value first and see if your web sites are now accessible.

To determine the correct setting, start with all MTU settings = 1500 and VPN = off. (VPN requires different testing).

In the terminal:

ping [-c count] [-M do] [-s packet_size] [host]

The options used are:

c count: number of times to ping
M hint: Select Path MTU Discovery strategy. may be either do (prohibit fragmentation, even local one), want (do PMTU discovery, fragment locally when packet size is large), or dont (do not set DF flag).
s packet_size: Specifies the number of data bytes to be sent.

You should always start at 1472 and work your way down by 10 each time. Once you get a reply, go up by 1 until you get a fragmented packet. Take that value (last good value) and add 28 to the value to account for the various TCP/IP headers. Eg. let's say that 1452 was the proper packet size (where you first got an ICMP reply to your ping). The actual MTU size would be 1480, which is the optimum for the network we're working with.

ping -c 4 -M do -s 1472 8.8.8.8 # this will probably show fragmentation

ping -c 4 -M do -s 1462 8.8.8.8 # may show fragmentation

ping -c 4 -M do -s 1452 8.8.8.8 # no fragmentation?

ping -c 4 -M do -s 1453 8.8.8.8 # still no fragmentation?

reference: How to determine the proper MTU size with ICMP pings

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Nate T

2/10/23, 8:39 PM

This is a good answer.

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Nate T

2/10/23, 8:48 PM

The "on and off" OP describes is classic Ubuntu weak-signal behavior. If only one device connection on the LAN loses conn., it will be the ubuntu card, and it will do it intermittently. Ive seen this across versions, across machines, and across networks. It is sort of an Achilles' heel for a very strong system.

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Imparo Ubuntu

2/15/23, 3:09 AM

@ Nate T . Is There any remedy to this issue?

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