10.3.4 Hardware considerations DVD/CD Drive Ethernet switches RSF is broadband-only 10.3.5 TCP/IP Version 6 on the HMC and SE The following HMC changes are important for z15: Starting with z15, a DVD/CD drive is not available with the HMC (nor with the SE). Ethernet switches for HMC and SE connectivity are provided by the client. Existing supported  switches can still be used. Ethernet switches and hubs often include the following characteristics: Note:  The recommendation is to use a switch with 1000 Mbps/Full duplex support. RSF through a modem is  not  supported the z15 HMC. Broadband is needed for hardware  problem reporting and service. For more information, see 10.4, “Remote  Support Facility” on  page 427. The HMC and SE can communicate by using IPv4, IPv6, or both. Assigning a static IP  address to an SE is unnecessary if the SE communicates only with the HMCs on the same  subnet. The HMC and SE can use IPv6 link-local addresses to communicate with each other. IPv6 link-local addresses feature the following characteristics: Since OSA/SF was moved from z/OS to HMC/SE environment, it was noted that it is no  longer easy to obtain a global view of all OSA PCHIDs and the monitoring and diagnostic  information that was available in the Query Host command. To address this issue, the following changes were made: 10.3.6 OSA Support Facility GLYPH<SM590000> No DVD/CD drive with HMC GLYPH<SM590000> IBM does not provide Ethernet switches with the system GLYPH<SM590000> RSF is broadband-only GLYPH<SM590000> A total of 16 auto-negotiation ports GLYPH<SM590000> 100/1000 Mbps data rate GLYPH<SM590000> Full or half duplex operation GLYPH<SM590000> Auto medium-dependent interface crossover (MDIX) on all ports GLYPH<SM590000> Port status LEDs GLYPH<SM590000> Every IPv6 network interface is assigned a link-local IP address. GLYPH<SM590000> A link-local address is used on a single link (subnet) only and is never routed. GLYPH<SM590000> Two IPv6-capable hosts on a subnet can communicate by using link-local addresses,  without having any other IP addresses assigned. GLYPH<SM590000> If a CPC is targeted, the initial window provides a global view of all OSA PCHIDs. GLYPH<SM590000> The user can browse to various OSA Advanced Facilities subtasks from the initial window,  which makes the process of getting to them less cumbersome. 424  IBM z15 (8561) Technical Guide