## 10.3.4 Hardware considerations 

The following HMC changes are important for z15: 

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 

## DVD/CD Drive 

Starting with z15, a DVD/CD drive is not available with the HMC (nor with the SE). 

## Ethernet switches 

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: 

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 

Note:  The recommendation is to use a switch with 1000 Mbps/Full duplex support. 

## RSF is broadband-only 

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. 

## 10.3.5 TCP/IP Version 6 on the HMC and SE 

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: 

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. 

## 10.3.6 OSA Support Facility 

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: 

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. 

