Unwanted route appears at every reboot...

nimrod

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Apr 27, 2022, 5:00:05 PM4/27/22

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Hi,

yesterday afternoon, after working all day at office without any (network) problem, I decided to reboot my machine. Suddenly I could not navigate on the web. But I could ping the gateway, I could resolve names... just cannot reach the network (most commands just issued the classic "network is unreachable" message).

thinking it was a route problem, I issued "ip route" on the terminal and got this default route:

default dev eno1 scope link src 169.254.30.62 metric 202

I deleted it and add the good one:

ip route add default via 192.168.1.113 dev eno1

and I could navigate again immediately. Nevertheless, after every reboot the wrong default route is there again. I couldn't find any file or directory in which this could be configured, nor I found a command that could create somehow implicitly such a default route.

How can prevent it to come back after reboot? I could add some kind of /etc/rc.local or a systemd target to remove the wrong one and add the right one at every boot, but i would prefer to understand why it happens. At least, since a 169.254 route is always on, I wish to undestand why it becomes the default one, preventing me from reach the internet.

Please note that I only use Network Manager from the Gnome GUI with a static address, and I didn't modify the configuration in several months. Never touched /etc/network* dirs and files, nor /etc/systemd/network.

Any hint will be much appreciated.

Best regards.

Jeremy Ardley

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Apr 27, 2022, 5:30:05 PM4/27/22

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On 28/4/22 4:49 am, nimrod wrote:
> default dev eno1 scope link src 169.254.30.62 metric 202
>
>

the 169.254 address is Used for link-local addresses between two hosts
on a single link when no IP address is otherwise specified, such as
would have normally been retrieved from a DHCP server.

So something is stopping your system from assigning the static address.

When it is booted and in the bad state what does 'ip a' show?

What does it show in syslog?

One suspicion is that another host on the LAN has the same address?

--
Jeremy

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Charles Curley

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Apr 27, 2022, 5:40:05 PM4/27/22

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On Wed, 27 Apr 2022 22:49:59 +0200
nimrod <nim...@paralog.it> wrote:

> Please note that I only use Network Manager from the Gnome GUI with a
> static address, and I didn't modify the configuration in several
> months. Never touched /etc/network* dirs and files, nor
> /etc/systemd/network.

Check that NM didn't somehow acquire a spurious route. Edit Connections
-> Your connection, little gear wheel in the lower left. IPv4 Settings
-> Routes.

Are you sure you aren't getting that spurious route from the DHCP
server? To check on that, add a short script to
/etc/NetworkManager/dispatcher.d, called, say, 50environment. It should
look something like

--------------------------------------------------
#!/bin/bash
LOG=/var/log/NetworkManager

{
echo "Environment is:"
printenv
route -n
} >> "${LOG}" 2>&1
--------------------------------------------------

Somewhere in that log file you should find a variable that specifies
extra routes, if any.

You can also check to be sure you are getting the correct
address. That should be in $IP4_ADDRESS. Mine looks like:

IP4_ADDRESS_0=192.168.100.44/24 192.168.100.31

I think the second address is either the DHCP server, or the DNS server.

The variables NM uses are detailed in man 8 networkmanager.

--
Does anybody read signatures any more?

https://charlescurley.com
https://charlescurley.com/blog/

David Wright

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Apr 28, 2022, 12:10:05 PM4/28/22

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It sounds as if your computer failed to find the DHCP server when you
rebooted "yesterday" afternoon, which could have made it autoconfigure
the interface with 169.254 (called ?mDNS), and add a route. There
doesn't seem to be a problem having these interfaces around unless
they get a default route.

I would look in /var/lib/avahi-autoipd/ and see if there's a file
called <your-eno1's-MAC> containing 169.254.30.62. If so, remove
it and, next time you reboot, it shouldn't happen. (That is, unless
you have a recurrence of the same problem as "yesterday" afternoon.)

I can simulate the same effect on a laptop by tapping its rfkill
switch when it boots, preventing the wifi from configuring.
Because /e/n/i still has a DHCP ethernet configuration festering
there as well as the wifi one, it sets an ethernet route that
obstructs the wifi's getting one when I un-rfkill the wifi.

As for the original cause, take a look at /var/log/daemon.log*
for "yesterday" afternoon with zgrep -i -e dhcp -e dhclient

Cheers,
David.

nim...@paralog.it

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Apr 29, 2022, 5:40:06 AM4/29/22

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On gio, 2022-04-28 at 05:26 +0800, Jeremy Ardley wrote:

On 28/4/22 4:49 am, nimrod wrote:

default dev eno1 scope link src 169.254.30.62 metric 202

the 169.254 address is Used for link-local addresses between two hosts
on a single link when no IP address is otherwise specified, such as
would have normally been retrieved from a DHCP server.

So something is stopping your system from assigning the static address.

When it is booted and in the bad state what does 'ip a' show?

"ip a" reports a normal situations in any case. At least, I could not see any oddities at this level, nor had I to change anything concerning just the ip addresses of my interfaces. The only interface I configured, only with NM, is eno1 with a static address:

1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000

link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00

inet 127.0.0.1/8 scope host lo