create-bridge.sh

#!/bin/bash

main() {

    IFace="${1}"
    MainIP="${2}"
    DNSList="${3}"
    BRIFace="${IFace}br"

    nmcli conn delete "System ${IFace}"

    nmcli conn add \
        type bridge \
        ifname "${BRIFace}" \
        autoconnect yes \
        con-name "${BRIFace}" \
        stp off

    nmcli conn modify "${BRIFace}" \
        ipv4.addresses "${MainIP}/24" \
        ipv4.gateway "${MainGateway}" \
        ipv4.dns "${DNSList}" \
        ipv4.method manual

    nmcli conn add \
        type bridge-slave \
        autoconnect yes \
        con-name "${IFace}" \
        ifname "${IFace}" \
        master "${BRIFace}"

    nmcli conn up "${BRIFace}"
}

main "$@"