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After upgrading from Ubuntu 16.04 LTS to the new 18.04, even before rebooting the system, ping won't work anymore. It just hangs indefinitely and doesn't matter if I ping a DNS, an IP or even the IP of a CentOS VM running in the same system. Now neither SSH is working. When I try to SSH into the VM, it hangs for a while up to the timeout.

Everything was working before.

I have internet working perfectly. I can curl anything, browse any website, install anything with apt. The only problem is that I need SSH working and it seems the ping problem is related to it.

I already checked my firewall, which is not rejecting anything, my ethernet configuration, which is auto by DHCP, and my hosts, which didn`t change from before upgrading.

My ethernet configuration:

> ifconfig | grep 'eno1:\|lo:' -A6
eno1: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        inet 10.121.3.143  netmask 255.255.255.0  broadcast 10.121.3.255
        inet6 fe80::4ff2:e79a:8a81:93e1  prefixlen 64  scopeid 0x20<link>
        ether dc:4a:3e:7d:f1:33  txqueuelen 1000  (Ethernet)
        RX packets 1007708  bytes 1386860256 (1.3 GB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 335796  bytes 30111660 (30.1 MB)
--
lo: flags=73<UP,LOOPBACK,RUNNING>  mtu 65536
        inet 127.0.0.1  netmask 255.0.0.0
        inet6 ::1  prefixlen 128  scopeid 0x10<host>
        loop  txqueuelen 1000  (Local Loopback)
        RX packets 3319  bytes 313220 (313.2 KB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 3319  bytes 313220 (313.2 KB)
> ▮

My route configuration:

> route
Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
default         _gateway        0.0.0.0         UG    100    0        0 eno1
10.121.3.0      0.0.0.0         255.255.255.0   U     100    0        0 eno1
link-local      0.0.0.0         255.255.0.0     U     1000   0        0 eno1
192.168.123.0   0.0.0.0         255.255.255.0   U     0      0        0 virbr0
> ▮

My hosts configuration:

> cat /etc/hosts                                                                                                                                                        
127.0.0.1       localhost
> ▮

My firewall configuration:

> sudo iptables -S
-P FORWARD ACCEPT
-P OUTPUT ACCEPT
-A INPUT -i virbr0 -p udp -m udp --dport 53 -j ACCEPT
-A INPUT -i virbr0 -p tcp -m tcp --dport 53 -j ACCEPT
-A INPUT -i virbr0 -p udp -m udp --dport 67 -j ACCEPT
-A INPUT -i virbr0 -p tcp -m tcp --dport 67 -j ACCEPT
-A FORWARD -d 192.168.123.0/24 -o virbr0 -m conntrack --ctstate RELATED,ESTABLISHED -j ACCEPT
-A FORWARD -s 192.168.123.0/24 -i virbr0 -j ACCEPT
-A FORWARD -i virbr0 -o virbr0 -j ACCEPT
-A OUTPUT -o virbr0 -p udp -m udp --dport 68 -j ACCEPT
> ▮

Here is the ping output to my VM's ip (192.168.122.12), which is on and I can access through virt-manager no problem:

> ping 192.168.122.12
PING 192.168.122.12 (192.168.122.12) 56(84) bytes of data.
▮

It stays there indefinitely.

However, it works if I ping localhost:

> ping localhost
PING localhost (127.0.0.1) 56(84) bytes of data.
64 bytes from localhost (127.0.0.1): icmp_seq=1 ttl=64 time=0.068 ms
64 bytes from localhost (127.0.0.1): icmp_seq=2 ttl=64 time=0.068 ms
64 bytes from localhost (127.0.0.1): icmp_seq=3 ttl=64 time=0.068 ms
^C
--- localhost ping statistics ---
3 packets transmitted, 3 received, 0% packet loss, time 2052ms
rtt min/avg/max/mdev = 0.068/0.068/0.068/0.000 ms
> ▮

Pinging to another machine on the same network also works:

> ping 10.121.3.41
PING 10.121.3.41 (10.121.3.41) 56(84) bytes of data.
64 bytes from 10.121.3.41: icmp_seq=1 ttl=64 time=0.580 ms
64 bytes from 10.121.3.41: icmp_seq=2 ttl=64 time=0.313 ms
64 bytes from 10.121.3.41: icmp_seq=3 ttl=64 time=0.277 ms
64 bytes from 10.121.3.41: icmp_seq=4 ttl=64 time=0.530 ms
64 bytes from 10.121.3.41: icmp_seq=5 ttl=64 time=0.248 ms
^C
--- 10.121.3.41 ping statistics ---
5 packets transmitted, 5 received, 0% packet loss, time 4097ms
rtt min/avg/max/mdev = 0.248/0.389/0.580/0.139 ms
> ▮

Pinging to an external website won't:

> ping www.google.com
PING www.google.com (172.217.30.36) 56(84) bytes of data.
▮

But that might be another issue related with my network manager. Again, I can browser no problem.

Here is the SSH output:

> ssh 192.168.122.12
▮

After some time:

> ssh 192.168.122.12
ssh: connect to host 192.168.122.12 port 22: Connection timed out
> ▮

Yes, the VM's port 22 is open for SSH connections (everything was working before the update):

(VM) > netstat -tuplen | grep "servers\|Proto\|:22 "
Active Internet connections (only servers)
Proto   Recv-Q   Send-Q   Local Address   Foreign Address    State   User   Inode   PID/program
tcp          0        0      0.0.0.0:22         0.0.0.0:*   LISTEN      0   18112     1295/sshd
tcp6         0        0           :::22              :::*   LISTEN      0   18114     1295/sshd
(VM) > ▮

Does anyone have any idea about how can I fix it?

* EDIT / SOLUTION *

Alright, forget it. I didn't check my VM's ip. Suddenly, it changed to another ip I don't know why. Checking ifconfig in VM gave me the right ip address.

I will keep the post for other people who may also forget to check it.

Thank you anyway.

  • @sebastian, thank you for the prompt reply. Sorry for not providing enough information before. I wasn't at the work at that time to provide the outputs. I edited the post. Now it should have enough information. – Teo May 22 '18 at 11:36

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