INTERNET PACKET (IP) FORWARDING

Packet forwarding is the process relaying of packets from one network segment to another by nodes in a computer network.  It can easily be implemented in CentOS 6.4 by enabling the following option in /etc/sysctl.conf file as follows :
# Kernel sysctl configuration file for Red Hat Linux

#

# For binary values, 0 is disabled, 1 is enabled.  See sysctl(8) and

# sysctl.conf(5) for more details.



# Controls IP packet forwarding

[root@dhcppc13 ~]# net.ipv4.ip_forward = 1
The above file can be opened in any editor (vim,nano,etc) preferred by the user.
User can confirm the settings  as below : 
[root@dhcppc13 ~]# /sbin/sysctl -p
The sample output is :
warning: /etc/sysctl.conf(7): invalid syntax, continuing...

net.ipv4.conf.default.rp_filter = 1

net.ipv4.conf.default.accept_source_route = 0

kernel.sysrq = 0

kernel.core_uses_pid = 1

net.ipv4.tcp_syncookies = 1

kernel.msgmnb = 65536

kernel.msgmax = 65536

kernel.shmmax = 68719476736

kernel.shmall = 4294967296