create_netns.sh

#!/bin/env bash

# Create network namespace
sudo ip netns add rimnet_1
sudo ip netns exec rimnet_1 ip link set dev lo up

sudo ip netns add rimnet_2
sudo ip netns exec rimnet_2 ip link set dev lo up

# Create the veth
sudo ip link add name veth0-rimnet type veth peer name veth0-rimnet-br
sudo ip link add name veth1-rimnet type veth peer name veth1-rimnet-br
sudo ip link add name veth2-rimnet type veth peer name veth2-rimnet-br

# Move the peer to rimnet_N
sudo ip link set veth1-rimnet netns rimnet_1
sudo ip link set veth2-rimnet netns rimnet_2

# Assign IPv4 address
sudo ip addr add 10.0.254.254/24 dev veth0-rimnet
sudo ip netns exec rimnet_1 sudo ip addr add 10.0.254.1/24 dev veth1-rimnet
sudo ip netns exec rimnet_2 sudo ip addr add 10.0.254.2/24 dev veth2-rimnet

# Create bridge from host to rimnet_1
sudo ip link add br-rimnet type bridge
sudo ip link set dev veth0-rimnet-br master br-rimnet
sudo ip link set dev veth1-rimnet-br master br-rimnet
sudo ip link set dev veth2-rimnet-br master br-rimnet

# Up
sudo ip link set veth0-rimnet up
sudo ip link set veth0-rimnet-br up
sudo ip netns exec rimnet_1 ip link set veth1-rimnet up
sudo ip link set veth1-rimnet-br up
sudo ip netns exec rimnet_2 ip link set veth2-rimnet up
sudo ip link set veth2-rimnet-br up
sudo ip link set br-rimnet up

# Configure routing
sudo iptables -t nat -A POSTROUTING --source 10.0.254.0/24 -j MASQUERADE
sudo iptables -t filter -A FORWARD -d 10.0.254.0/24 -j ACCEPT

sudo ip netns exec rimnet_1 ip route add default via 10.0.254.254
sudo ip netns exec rimnet_2 ip route add default via 10.0.254.254

# Configure firewall
if ! command -v firewall-cmd &> /dev/null
then
    exit
fi

firewall-cmd --add-port=7891/udp