custom_dds_profile.xml

<?xml version="1.0" encoding="UTF-8" ?>
<dds xmlns="http://www.eprosima.com">
    <profiles>
        <transport_descriptors>
            <transport_descriptor>
                <transport_id>udp_transport</transport_id>
                <type>UDPv4</type>
            </transport_descriptor>
            <transport_descriptor>
                <transport_id>shm_transport</transport_id>
                <segment_size>10485760</segment_size>
                <maxMessageSize>5242880</maxMessageSize>
                <type>SHM</type>
            </transport_descriptor>
        </transport_descriptors>
        <participant profile_name="default" is_default_profile="true">
            <rtps>
                <!--
                    Set participant transports
                -->
                <userTransports>
                    <!--
                        Documentation: 
                        https://fast-dds.docs.eprosima.com/en/latest/fastdds/transport/transport.html#comm-transports-configuration
                    -->
                    <transport_id>udp_transport</transport_id>
                    <transport_id>shm_transport</transport_id>
                </userTransports>
                <useBuiltinTransports>false</useBuiltinTransports>
           </rtps>
        </participant>
    </profiles>
</dds>