Creates a network namespace and a network connection between that and the current namespace. Can run multiple servers on the same port and all interfaces

create_network_namespaces.sh

#!/bin/bash

if (( $EUID != 0 )); then
    echo "Please run this as sudo $0" >&2
    exit 1
fi

function create_space {

    NS=$1
    ETH=$2
    IP_LOCAL=$3
    IP_REMOTE=$4
    BRIDGE=$5
    DEFAULT_GATEWAY=$6

    # Create a new network namespace
    ip netns add $NS
    # Bring loopback interface up in the namespace
    ip netns exec $NS ip link set dev lo up

    # Create a veth interface with two ends
    ip link add ${ETH}host type veth peer name ${ETH}remote
    # move one end into the other namespace
    ip link set ${ETH}remote netns $NS

    # Assign an ip address and bring the interface up in the namespace
    ip netns exec $NS ip addr add ${IP_REMOTE}/24 dev ${ETH}remote
    ip netns exec $NS ip link set ${ETH}remote up
    ip netns exec $NS ip route add default via $DEFAULT_GATEWAY

    # Assign an ip address and bring the interface up in the current namespace
    ip addr add ${IP_LOCAL}/24 dev ${ETH}host
    ip link set ${ETH}host up
    # connect it to the bridge
    ip link set ${ETH}host master $BRIDGE
}


ip link add br0 type bridge
ip addr add 192.168.0.1/24 dev br0
ip link set br0 up

create_space netns1 veth1_ 192.168.0.2 192.168.0.3 br0 192.168.0.1
create_space netns2 veth2_ 192.168.0.4 192.168.0.5 br0 192.168.0.1

# sudo ip link delete br0
# sudo ip netns list | awk '{print $1}' | sudo xargs ip netns delete