network related commands suddenly stopped working

Question

Debian GNU/Linux 9.12 (stretch) Release: 9.12

Today I realized that a few network related commands suddenly stopped working. For example: pin, host, iptables, dig and so on, they don't work anymore.

Here's the output of route -n, for example

root@host5:~# route -n
Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
0.0.0.0         192.168.104.153 0.0.0.0         UG    0      0        0 ens160
192.168.104.152 0.0.0.0         255.255.255.248 U     0      0        0 ens160
root@host5:~# ping 192.168.104.153
PING 192.168.104.153 (192.168.104.153) 56(84) bytes of data.
^C
--- 192.168.104.153 ping statistics ---
7 packets transmitted, 0 received, 100% packet loss, time 6127ms

ifconfig command output

root@fhost5:~# ifconfig
ens160: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        inet 192.168.104.156  netmask 255.255.255.248  broadcast 192.168.104.159
        inet6 fe80::250:56ff:fe88:3d72  prefixlen 64  scopeid 0x20<link>
        ether 00:50:56:88:3d:72  txqueuelen 1000  (Ethernet)
        RX packets 4581  bytes 910358 (889.0 KiB)
        RX errors 0  dropped 13  overruns 0  frame 0
        TX packets 4562  bytes 417363 (407.5 KiB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0


host IP address: 192.168.104.156
network segment: 192.168.104.152/29

Actually I cannot ping the gateway. But from another host on the same network segment, the gateway is reachable

I was thinking that the issue is somewhat related to the system ...I mean a local issue All the network commands seem to be stuck You know I run iptables and nothing happens, the same with host ..etc

root@host5:~# host google.com
^Croot@host5:~#

Unfortunately I got nowhere.

Any help will be highly appreciated

does this also happen when you work with IP-Adresses instead of hostnames. for example: does #> ping 8.8.8.8 and #> ping 192.168.104.156 work? — Marc, Jan 11 '21 at 18:08
but the network connections of this machine is still working? you connected to it via ssh? you can ping it from another machine? — Marc, Jan 11 '21 at 19:14
dmesg or other system logs don't show any clues? Always look there when system starts behaving very strange. — Nikita Kipriyanov, Jan 11 '21 at 20:08
I can access the machine through ssh...dmesg shows many things like [ 10.892307] EXT4-fs (sda1): mounting ext2 file system using the ext4 subsystem [ 10.928221] EXT4-fs (sda1): mounted filesystem without journal. Opts: (null) [ 20.194301] ip6_tables: (C) 2000-2006 Netfilter Core Team [ 20.424976] vmxnet3 0000:03:00.0 ens160: intr type 3, mode 0, 5 vectors allocated [ 20.426346] vmxnet3 0000:03:00.0 ens160: NIC Link is Up 10000 Mbps what should I look for.. another important thing I cannot ping it from another host — iques, Jan 11 '21 at 21:08
also dmesg shows: 0.368068] pci 0000:00:17.6: BAR 13: failed to assign [io size 0x1000] 42 messages like this — iques, Jan 11 '21 at 22:00
Is anyone willing to help me? Is something related to the kernel? — iques, Jan 12 '21 at 06:56
related to Nikitas suggestion to check the `dmesg` output: run one of the network commands that hang, then check with `dmesg` if there are new kernel log messages. you could also try to install "strace" (`apt install strace` on debian or ubuntu machines) and run something link `strace ping 8.8.8.8` and check if this gives you a clue what the program was trying to do, the moment it started to hang. have you checked if the non-working binaries or other binaries have been changed recently? `ls -l \`which ping\`` `dpkg --verify` `` — Marc, Jan 12 '21 at 09:23
thanks Marc...I cannot ping any host..every network related command just hangs...other tools seem to be working (I mean I can start them i though they run very slowly...) what about a kernel roll back? do you think that would be a good idea? — iques, Jan 12 '21 at 10:58

network related commands suddenly stopped working

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