Boolean isTrustedIp = false;

    Map<String, String> sessionAttributes;
    try {
        sessionAttributes = Auth.SessionManagement.getCurrentSession();
    } catch(Exception e) {
        isTrustedIp = false;
        // TODO handle unexpected error...
    }

    String sourceIP = sessionAttributes.get('SourceIp');
    if(sourceIp != null) {
        isTrustedIp = Auth.SessionManagement.inOrgNetworkRange(sourceIP);
    }

    // TODO do something with isTrustedIp...