DXF to IGS is one of the most common CAD conversions and since most CAD programs support both the DXF and IGS format you should have no trouble finding one that suits your needs. Almost every modern CAD tool or dedicated CAD converter should be capable of dxf to igs conversion just fine.
Open DXF file Open IGS fileA CAD viewer program with conversion capabilities
A CAD and Gerber conversion software
A set of 3D modeling tools
A 3D modelling software
3D CAD/CAM tool for product development
A CAD converter with huge format support
A CAD/CAM for material working industry
An open source multiplatform 3D CAD/MCAD/CAx/CAE/PLM modeler
A dedicated 2D/3D CAD software
A 3D CAD translation software
A suite of CAD applications
A CAD drawing and CNC programming system