Offline: IP address available but neither ping nor nslookup to local network nor internet possible

[Christling]

Hello,
I’ve been using my Manjaro since 2020 and except for a few small things, I’ve always been very happy with it and managed everything on my own when there was something wrong. Until today.

After a reboot I can’t reach any clients in the 192.168.5.0/24 network anymore. But funny enough in the management network (192.168.40.0/24). The name resolution with nslookup does not work.

Except for a replacement of iptables by iptables-nft during an installation there was no reason to suspect something like that. I checked before via Google if iptables-nft could cause problems. It did not look like that. Then came the reboot and now this. :-/ Iptables-nft removed and iptables reinstalled. Unfortunately, the PC is my work PC on which I emulate Windows (virt-manager), so it is already pressing me very much.

UFW is disabled. Iptables was stopped and restarted.

Can anyone help here? What can this be?

.
update: I am writing here from another computer.

[Mirdarthos]

Hi @Christling,

It won’t surprise me if I’m wrong, but it sounds like you gateway and DNS servers aren’t set.

What is the output of:

cat /etc/resolv.conf

Also please provide the output of:

ip a

Edit:

Also please post the output of:

ifconfig

And

ip r

[Christling]

Thank you for your support!
I can only provide the information via images.

ip r:

First time I took a photo of my screen instead of capture it.

[Mirdarthos]

@Christling

ip r:

Once again, I might be wrong, so I plead innocent if I am, and if you continue, it’s at own risk.

Compared to mine:

$ ip r
default via 10.0.0.1 dev enp0s31f6 proto dhcp src 10.0.0.20 metric 100
10.0.0.0/24 dev enp0s31f6 proto kernel scope link src 10.0.0.20 metric 100

…your routes seem messed up. Either that, or there’s a computer missing that should be there, because it seems all your traffic gets routed thorough the 192.168.5.254 IP address.

So, let’s dig a bit deeper. Please provide the output of:

route -n

…and hope we don’t reach the end of my knowledge before we find an answer.

(P.S.: The pictures are OK in this case.)

[Christling]

Just FYI - I didn’t changed anything regarding the network configuration or dhcp:

route -n

Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
0.0.0.0         192.168.5.254   0.0.0.0         UG    100    0        0 eno1
192.168.5.0     192.168.5.254   255.255.255.0   UG    100    0        0 eno1
192.168.5.0     0.0.0.0         255.255.255.0   U     100    0        0 eno1

[Mirdarthos]

Just as I thought:

Once again, I might be wrong, but it looks to me, like your routing is wonky. Not saying you changed it, but it looks wonky, as if your PC is trying to route all network traffiv through the device at the 192.168.5.254 IP.

Compared to mine:

$ route -n
Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
0.0.0.0         10.0.0.1        0.0.0.0         UG    100    0        0 enp0s31f6
10.0.0.0        0.0.0.0         255.255.255.0   U     100    0        0 enp0s31f6

…my guess would be you have to delete the one in the middle.

And according to your previous reply,

… deleting the one in the middle should simply be a matter of:

route delete 192.168.5.0/24 via 192.168.5.254

Note:

AFAIK this isn’t permanent, and a reboot should restore it to its current state. So if it doesn’t work, simply reboot. If it does work, however, it needs to be made permanent.

Further reading:

https://wiki.archlinux.org/title/Network_configuration#Routing_table

[Christling]

route delete 192.168.5.0:24 via 192.168.5.254

or

route del 192.168.5.0:24 via 192.168.5.254 dev eno1

192.168.5.0:24: Unknown host

[andreas85]

find the error:

try:

 ip route delete ...

instead of

route delete ...

[Christling]

route del 192.168.5.0/24 via 192.168.5.254
Usage: inet_route [-vF] del {-host|-net} Target[/prefix] [gw Gw] [metric M] [[dev] If]
       inet_route [-vF] add {-host|-net} Target[/prefix] [gw Gw] [metric M]
                              [netmask N] [mss Mss] [window W] [irtt I]
                              [mod] [dyn] [reinstate] [[dev] If]
       inet_route [-vF] add {-host|-net} Target[/prefix] [metric M] reject
       inet_route [-FC] flush      NOT supported

“/” doesn’t work this was the reason I used “:”.

[Mirdarthos]

OK, I’m also confused now. So let’s start at the beginning.

Please provide the output for:

ip route show

[Mirdarthos]

@andreas85

try:

 ip route delete ...

instead of

route delete ...

At this point in time, might as well…

[Christling]

I am back online! I will take care of a permanent solution, Thank you very much!