Other ISM considerations More information ISM systems include the following limits: For more information about a configuration example for SMC-D, see  IBM z/OS V2R2  Communications Server TCP/IP Implementation - Volume 1 , SG24-8360. GLYPH<SM590000> A total of 32 ISM VCHIDs (in IOCDS/HCD) per CPC. Each IOCDS/HCD VCHID  represents a unique internal shared memory network each with a unique Physical  Network ID. GLYPH<SM590000> A total of 255 VFs per VCHID (8k VFs per CPC). For example, the maximum number of  virtual servers that can communicate over the same ISM VCHID is 255. GLYPH<SM590000> Each ISM VCHID in IOCDS/HCD represents a unique (isolated) internal network, each  having a unique Physical Network ID (PNet IDs are configured in HCD/IOCDS). GLYPH<SM590000> ISM VCHIDs support VLANs (can be subdivided into VLANs). GLYPH<SM590000> ISM provides a GID (internally generated) to correspond with each ISM FID. GLYPH<SM590000> All MACs (VMACs), MTU, physical ports, and Frame sizes are not applicable. GLYPH<SM590000> ISM is supported by z/VM (for pass-through guest access to support the new PCI  function). 500  IBM z14 (3906) Technical Guide