You need to enable IPv4 Forwarding. There is an excellent write up on the subject here.
The following will help you check the system state and set the parameter from the command line. Please note, this setting will be ephemeral; you will need to determine how to make the setting permanent (if you so wish) based upon your specific distribution and version.
The following is taken from this article:
Check if IP Forwarding is enabled
We have to query the sysctl kernel value net.ipv4.ip_forward to see if forwarding is enabled or not:
net.ipv4.ip_forward = 0
or just checking out the value in the /proc system:
As we can see in both the above examples this was disabled (as show by the value 0).
Enable IP Forwarding on the fly
As with any sysctl kernel parameters we can change the value of net.ipv4.ip_forward on the fly (without rebooting the system):
sysctl -w net.ipv4.ip_forward=1
echo 1 > /proc/sys/net/ipv4/ip_forward
the setting is changed instantly; the result will not be preserved after rebooting the system.