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.

Answer 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

Answer 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

Answer 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

Answer 4

In my case, if your system is behind a firewall, that can't interact with internet. Unless you specify a proxy server for HTTP/HTTPS/FTP, it is not reachable.

Try this:

export  http_proxy=http://yourcompanyproxy.company.com:1234   
export  ftp_proxy=ftp://yourcompanyproxy.company.com:1234  
export  https_proxy=https://yourcompanyproxy.company.com:1234