mjhjmtu

I have a small cluster with several nodes. Only one node (let's call it root), can connect to the internet. All nodes are connected, so we can ping from one to another, but we can't reach Internet from common node (i.e. not root).

Root node ifconfig output:

eth0 Link encap:Ethernet HWaddr b8:27:eb:d8:53:25 
 inet addr:192.168.10.10 Bcast:192.168.10.255 Mask:255.255.255.0
 UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
 RX packets:4084 errors:0 dropped:1295 overruns:0 frame:0
 TX packets:841 errors:0 dropped:0 overruns:0 carrier:0
 collisions:0 txqueuelen:1000 
 RX bytes:249141 (243.3 KiB) TX bytes:87110 (85.0 KiB)

eth1 Link encap:Ethernet HWaddr b8:8d:12:54:75:aa 
 inet addr:158.184.27.129 Bcast:158.184.27.255 Mask:255.255.255.0
 UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
 RX packets:1647 errors:0 dropped:0 overruns:0 frame:0
 TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
 collisions:0 txqueuelen:1000 
 RX bytes:229772 (224.3 KiB) TX bytes:68634 (67.0 KiB)

lo Link encap:Local Loopback 
 inet addr:127.0.0.1 Mask:255.0.0.0
 UP LOOPBACK RUNNING MTU:65536 Metric:1
 RX packets:4 errors:0 dropped:0 overruns:0 frame:0
 TX packets:4 errors:0 dropped:0 overruns:0 carrier:0
 collisions:0 txqueuelen:0 
 RX bytes:260 (260.0 B) TX bytes:260 (260.0 B)

wlan0 Link encap:Ethernet HWaddr 00:0f:13:39:02:c3 
 inet addr:158.196.122.94 Bcast:158.196.123.255 Mask:255.255.252.0
 UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
 RX packets:127 errors:0 dropped:0 overruns:0 frame:0
 TX packets:75 errors:0 dropped:0 overruns:0 carrier:0
 collisions:0 txqueuelen:1000 
 RX bytes:37269 (36.3 KiB) TX bytes:27150 (26.5 KiB)

Root node route -n output

Kernel IP routing table
Destination Gateway Genmask Flags Metric Ref Use Iface
default 158.184.27.1 0.0.0.0 UG 0 0 0 eth1
158.184.27.0 * 255.255.255.0 U 0 0 0 eth1
192.168.10.0 * 255.255.255.0 U 0 0 0 eth0

Common node ifconfig output:

eth0 Link encap:Ethernet HWaddr b8:27:eb:b3:ed:0e 
 inet addr:192.168.10.11 Bcast:192.168.10.255 Mask:255.255.255.0
 UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
 RX packets:5078 errors:0 dropped:2249 overruns:0 frame:0
 TX packets:1502 errors:0 dropped:0 overruns:0 carrier:0
 collisions:0 txqueuelen:1000 
 RX bytes:287740 (280.9 KiB) TX bytes:179477 (175.2 KiB)

lo Link encap:Local Loopback 
 inet addr:127.0.0.1 Mask:255.0.0.0
 UP LOOPBACK RUNNING MTU:65536 Metric:1
 RX packets:36 errors:0 dropped:0 overruns:0 frame:0
 TX packets:36 errors:0 dropped:0 overruns:0 carrier:0
 collisions:0 txqueuelen:0 
 RX bytes:3590 (3.5 KiB) TX bytes:3590 (3.5 KiB)

Common node route -n output:

Kernel IP routing table
Destination Gateway Genmask Flags Metric Ref Use Iface
0.0.0.0 192.168.10.10 0.0.0.0 UG 0 0 0 eth0
192.168.10.0 0.0.0.0 255.255.255.0 U 0 0 0 eth0

Do you have any idea, how could I connect to the Internet from common node through the root node? I have very little knowledge of networking, so please, try to explain it in detail.

EDIT:

Considering Richard Neumann's answer, I enabled IP forwarding on the root node. And I think, that the root node already IS set as the default gateway (see Common node route -n output).

But the internet is still not working...

EDIT 2:

> traceroute 8.8.8.8
1 permonik0 (192.168.10.10) 0.972ms 0.957ms 0.922ms
2 * * *
...
30 * * *

EDIT 3:

I set NAT up according to this article and now I can even ping 8.8.8.8 successfully. But still, I can't ping any website, so it looks, there is some remaining DNS problem now.

If @Richard Neumann's answer did not work, there is a possibility of it being a DNS issue.

echo "nameserver 8.8.8.8" >> /etc/resolv.conf

Set up IP Forwarding and Masquerading.

iptables -P FORWARD ACCEPT
iptables --table nat -A POSTROUTING -o eth1 -j MASQUERADE
iptables --table nat --append POSTROUTING --jump MASQUERADE --source 192.168.10.10/24 
iptables-save > /root/clients.fw
echo "/sbin/iptables-restore < /root/clients.fw" >> /etc/rc.local

This above commands will enable IP Forwarding, and setup a firewall using iptables that allows you to access the internet from your client's.

Your root node will have to act as a router for the other nodes.

You'll need to enable IP forwarding, in your case for IPv4, on the router:

sysctl -w net.ipv4.ip_forward = 1

And to make it persistent, edit /etc/sysctl.conf and set:

net.ipv4.ip_forward=1

You'd probably also want to make the router the default gateway on the other nodes.

If the next hop beyond your router is not aware of the network 192.168.10.10/24, then you'll need to implement Network Address Translation (NAT).

Have a look at iptables and its MASQUERADE option.

For possible DNS issues, see @Hunter.S.Thompson's answer.