How to access internal from external?

I have two network interfaces on a node. One is internal network and the other is external network. Internal network is 192.168.50.0/255.255.255.0(internal network). And external network is 192.168.0.0/255.255.255.0. Kubernetes consists of 192.168.50.0/255.255.255.0. I want to approach internal network from another local nodes without using internal network interface. How can I solve this problem?

Solution

Without subnet masks , I do not understand how they are different networks.

But , in any case , you need to enable routing packets from one interface to another. I assume you are on Linux node , there you may enable ip-forwarding.

echo 1 >> /proc/sys/net/ipv4/ip_forward

Then set up some rules in iptables to perform the natting and forwarding:

Example rules:

# Always accept loopback traffic
iptables -A INPUT -i lo -j ACCEPT

# We allow traffic from the LAN side
iptables -A INPUT -i eth0 -j ACCEPT

######################################################################
#
#                         ROUTING
#
######################################################################

# eth0 is LAN
# eth1 is WAN

# Allow established connections
iptables -A INPUT -m state --state ESTABLISHED,RELATED -j ACCEPT
# Masquerade.
iptables -t nat -A POSTROUTING -o eth1 -j MASQUERADE
# fowarding
iptables -A FORWARD -i eth1 -o eth0 -m state --state RELATED,ESTABLISHED -j ACCEPT
# Allow outgoing connections from the LAN side.
iptables -A FORWARD -i eth0 -o eth1 -j ACCEPT

https://serverfault.com/questions/453254/routing-between-two-networks-on-linux