On 3/12/23 11:30, Roger Heflin wrote:
On Sat, Dec 2, 2023 at 3:16 PM <fedora@xxxxxxxxxxxxxx> wrote:
On 3/12/23 00:43, Roger Heflin wrote:
My experience with the MTU being wrong is that often nothing works to
inform the sending end that the MTU is wrong.
The MTU being wrong (and below 1500) is not an expected/handled
condition for the TCP stack. meaning it will break for anything that
uses a MTU above the size, especially if the wrong MTU is a few
byte(or more) than any advertised MTU in the path.
So what does your network diagram look like?
A rather simple setup.
server
\ \
\ eth1 192.168.2.7 --- 192.168.2.5 - modem --- 4G
eth0 192.168.3.7 --- switch -- home network
modem is TP-Link VX420-G2h supplied by the ISP.
My main clue is that everything worked for a year with this modem,
then unexpectedly, overnight, the problem appeared and still persist.
[trimmed]
Have you logged into the modem and checked if it has any settings?
I cannot log in, but the menu offered by the modem does not show any relevant settings.
You might also test a device on wifi and/or login to the router and
send a test ping from inside the router with a large size.
WiFi is turned off on the modem, but I might give it a try.
What does the network config for 192.168.2.7 look like? And you do
the pings from the server connected to both?
$ ifconfig eth1
eth1: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 1456
inet 192.168.2.7 netmask 255.255.255.0 broadcast 192.168.2.255
ether 00:1b:21:3a:56:72 txqueuelen 1000 (Ethernet)
RX packets 4009354 bytes 4646140675 (4.3 GiB)
RX errors 0 dropped 0 overruns 0 frame 0
TX packets 1465729 bytes 195820660 (186.7 MiB)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0
device interrupt 18 memory 0x515c0000-515e0000
I do the pings and tracepath from this server.
It could be the reason no one else is seeing this is that they are not
using the wired network and that is what they screwed up.
The ISP finally confirmed that other users have issues too. Good news I guess?
--
Eyal at Home (fedora@xxxxxxxxxxxxxx)
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