connect: Network is unreachable? - ping

Question

When I attempt to ping google's dns or any outside the network I get connect: Network is unreachable?

I can't update either which I put down to this

I am new to networking... And Ubuntu. But these are results of some commands I thought might help

$ ip a
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN 
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
    inet 127.0.0.1/8 scope host lo
    inet6 ::1/128 scope host 
       valid_lft forever preferred_lft forever
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq state UP qlen 1000
    link/ether 00:0e:7f:a9:10:54 brd ff:ff:ff:ff:ff:ff
    inet 192.168.0.5/24 brd 192.168.0.255 scope global eth0
    inet6 fe80::20e:7fff:fea9:1054/64 scope link 
       valid_lft forever preferred_lft forever
3: virbr0: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc noqueue state DOWN 
    link/ether 86:0b:cb:43:63:a5 brd ff:ff:ff:ff:ff:ff
    inet 192.168.122.1/24 brd 192.168.122.255 scope global virbr0
mcserver@helloworld:~$ 

$ vi /etc/resolv.conf:
# Dynamic resolv.conf(5) file for glibc resolver(3) generated by resolvconf(8)
#     DO NOT EDIT THIS FILE BY HAND -- YOUR CHANGES WILL BE OVERWRITTEN
nameserver 192.168.0.5
nameserver 8.8.8.8

$ vi /etc/network/interfaces
# The loopback network interface
auto lo
iface lo inet loopback

# The primary network interface
auto eth0
iface eth0 inet static
        address 192.168.0.5
        netmask 255.255.255.0
        network 192.168.1.0
        broadcast 192.168.0.255
        post-up iptables-restore < /etc/iptables.up.rules
        dns-nameservers 192.168.0.5 8.8.8.

Solution 1

The following line is wrong:

iface eth0 inet static
    address 192.168.0.5
    netmask 255.255.255.0
    network 192.168.1.0 <<<<<<<<<<<<<<<<<<<<<<<< It should be 192.168.0.0
    broadcast 192.168.0.255
    post-up iptables-restore < /etc/iptables.up.rules
    dns-nameservers 192.168.0.5 8.8.8.8

Also, there doesn't seem to be any default gateway setup.

Not having more info about your network, I would suggest adding the following line at the end:

    gateway <YOUR.ROUTER.IP.ADDRESS>

So, assuming your router ip address is 192.168.0.1, this would be the whole entry:

iface eth0 inet static
    address 192.168.0.5
    netmask 255.255.255.0
    network 192.168.0.0
    broadcast 192.168.0.255
    post-up iptables-restore < /etc/iptables.up.rules
    gateway 192.168.0.1
    dns-nameservers 192.168.0.5 8.8.8.8

Solution 2

The problem is that you need to set your default gateway

1. Take terminal

2. Type in

   sudo ip route add default via <your gateway>(eg:192.168.136.1) dev eth0
   

3. Sometimes you will be able to ping (ping 8.8.8.8) but no internet connection in the browser, then:

4. Go to sudo nano /etc/resolv.conf

5. Add nameserver 8.8.8.8

6. Add nameserver <your gateway> or nameserver 127.0.1.1

7. sudo /etc/init.d/networking restart or sudo service networking restart

Solution 3

You may need to add a default gateway. As a root user, execute this command.

E.g.

root@localhost:~# route add default gw 172.23.5.1

You can get the first 3 octets, 172.23.5 from eth0/eoM

Then ping an IP to see if connection works.

root@localhost:~# ping 10.56.94.81    
PING 10.56.94.81 (10.56.94.81) 56(84) bytes of data.    
64 bytes from 10.56.94.81: icmp_seq=1 ttl=62 time=0.203 ms    
64 bytes from 10.56.94.81: icmp_seq=2 ttl=62 time=0.197 ms    
64 bytes from 10.56.94.81: icmp_seq=3 ttl=62 time=0.210 ms    
^C    
--- 10.56.94.81 ping statistics ---    
3 packets transmitted, 3 received, 0% packet loss, time 2033ms    
rtt min/avg/max/mdev = 0.197/0.203/0.210/0.012 ms

Comments

[GnP]

What's the output of ip route show

[user240010]

192.168.0.0/24 dev eth0 proto kernel scope link src 192.168.0.5 192.168.122.0/24 dev virbr0 proto kernel scope link src 192.168.122.1

[GnP]

ip route add default via 192.168.0.1 dev eth0 should get you connectivity, assuming your routers ip address is 192.168.0.1. If this works (try ping 8.8.8.8 first, then google.com) check my answer for persisting the changes.

[Frank]

@GnP, You wrote an excellent and clever solution. I discovered just now that it does not persist after logout. Could you please tell me how to persist it? Thanks.

[GnP]

@Frank I'm not sure I understand the question. Network configuration isn't affected by login/logout except in very particular circumstances (nm+wifi maybe). The answer I posted below is a /etc/network/interfaces entry, which is persistent accross reboots.

[Frank]

@GnP, Thank you for your reply tonight. I tested the 1 answer below and it had no effect after logout and login. I really admired your ip route add default via 192.168.0.1 dev eth0 idea that it should get you connectivity, assuming your routers ip address is 192.168.0.1. . How might we make it persist?

[Frank]

@GnP, I made the mistake of editing my network connection to automatic DHCP which forces a renewal of DHCP lease after logout and relogin and destroys persistence across reboots. How could I fix that mistake on my part? Thank you.'

[GnP]

@Frank depends on what you did, what type of connection, etc. You should ask a new question, posting your current config and whatever else you find relevant.

[Kiran Reddy]

superuser.com/a/667800/476079

[Kiran Reddy]

Finally, the below helped me resolve the issue datawookie.netlify.com/blog/2018/10/dns-on-ubuntu-18.04

[Marc Vanhoomissen]

Welcome to askubuntu. Two remarks: 1. Refrain answering questions with an accepted answer unless you really come with something different. 2. Never advise to sudo su, as this is considered bad practice here for many reasons.