How to set up a gateway based on CentOS 6.8 with OpenVPN?

Question

openvpn

Good afternoon.
There is a Centos 6.8 server with the address 172.19.1252.95.
It has openvpn installed.
How to configure the server so that clients on the 172.19.252.0/24 network can go to the addresses available after the tunnel is established?

[vpn ~]# ifconfig
eth0 Link encap:Ethernet HWaddr 00:50:56:A9:30:9C
inet addr:172.19.252.95 Bcast:172.19.255.255 Mask:255.255.252.0
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:131081 errors:0 dropped:0 overruns:0 frame:0
TX packets:3236 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:9731034 (9.2 MiB) TX bytes:461938 ( 451.1 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:0 errors:0 dropped:0 overruns:0 frame:0
TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:0 (0.0 b) TX bytes:0 (0.0 b)
tun0 Link encap:UNSPEC HWaddr 00-00-00- 00-00-00-00-00-00-00-00-00-00-00-00-00
inet addr:172.31.0.190 PtP:172.31.0.189 Mask:255.255.255.255
UP POINTOPOINT RUNNING NOARP MULTICAST MTU:1500 Metric :1
RX packets:410 errors:0 dropped:0 overruns:0 frame:0
TX packets:1064 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:100
RX bytes:81564 (79.6 KiB) TX bytes :64038 (62.5 KiB)

[vpn ~]# iptables -L -v -n
Chain INPUT (policy ACCEPT 1287 packets, 217K bytes)
pkts bytes target prot opt ​​in out source destination
166 21668 ACCEPT all -- * * 0.0.0.0/0 0.0.0.0/0 state RELATED,ESTABLISHED
0 0 ACCEPT icmp -- * * 0.0.0.0/0 0.0.0.0/0
0 0 ACCEPT all -- lo * 0.0.0.0/0 0.0.0.0/0
0 0 ACCEPT tcp -- * * 0.0. 0.0/0 0.0.0.0/0 state NEW tcp dpt:22
Chain FORWARD (policy ACCEPT 117 packets, 7020 bytes)
pkts bytes target prot opt ​​in out source destination
Chain OUTPUT (policy ACCEPT 166 packets, 24970 bytes)
pkts bytes target prot opt ​​in out source destination

[vpn ~]# cat /etc/sysctl.conf
# 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.
#
# Use '/sbin/sysctl -a' to list all possible parameters.
# Controls IP packet forwarding
net.ipv4.ip_forward = 1
# Controls source route verification
net.ipv4.conf.default.rp_filter = 1
# Do not accept source routing
net.ipv4.conf.default.accept_source_route = 0
# Controls the System Request debugging functionality of the kernel
kernel.sysrq = 0
# Controls whether core dumps will append the PID to the core filename.
# Useful for debugging multi-threaded applications.
kernel.core_uses_pid = 1
# Controls the use of TCP syncookies
net.ipv4.tcp_syncookies = 1
# Controls the default maxmimum size of a mesage queue
kernel.msgmnb = 65536
# Controls the maximum size of a message, in bytes
kernel.msgmax = 65536
# Controls the maximum shared segment size, in bytes
kernel.shmmax = 68719476736
# Controls the maximum number of shared memory segments, in pages
kernel.shmall = 4294967296
net.ipv6.conf.all.disable_ipv6 = 1
net.ipv6.conf.default .disable_ipv6 = 1
net.ipv4.conf.default.forwarding = 1