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Cisco MDS 9000 Family NX-OS Interfaces Configuration Guide
OL-29284-01, Release 6.x
Chapter 1 Interfaces Overview
Extended Credits
Extended Credits
Full line-rate Fibre Channel ports provide at least 255 buffer credits standard. Adding credits lengthens
distances for Fibre Channel SAN extension. Using extended credits, up to 4095 buffer credits from a
pool of more than 6000 buffer credits for a module can be allocated to ports as needed to greatly extend
the distance for Fibre Channel SANs.
N Port Virtualization
Cisco NX-OS software supports industry-standard N port identifier virtualization (NPIV), which allows
multiple N port fabric logins concurrently on a single physical Fibre Channel link. HBAs that support
NPIV can help improve SAN security by enabling zoning and port security to be configured
independently for each virtual machine (OS partition) on a host. In addition to being useful for server
connections, NPIV is beneficial for connectivity between core and edge SAN switches.
N port virtualizer (NPV) is a complementary feature that reduces the number of Fibre Channel domain
IDs in core-edge SANs. Cisco MDS 9000 family fabric switches operating in the NPV mode do not join
a fabric; they only pass traffic between core switch links and end devices, which eliminates the domain
IDs for these switches. NPIV is used by edge switches in the NPV mode to log in to multiple end devices
that share a link to the core switch. This feature is available only for Cisco MDS Blade Switch Series,
the Cisco MDS 9124 Multilayer Fabric Switch, and the Cisco MDS 9134 Multilayer Fabric Switch.
FlexAttach
Cisco NX-OS supports the FlexAttach feature. One of the main problems in a SAN environment is the
time and effort required to install and replace servers. The process involves both SAN and server
administrators, and the interaction and coordination between them can make the process time
consuming. To alleviate the need for interaction between SAN and server administrators, the SAN
configuration should not be changed when a new server is installed or an existing server is replaced.
FlexAttach addresses these problems, reducing configuration changes and the time and coordination
required by SAN and server administrators when installing and replacing servers. This feature is
available only for Cisco MDS 9000 Blade Switch Series, the Cisco MDS 9124, and the Cisco MDS 9134
when NPV mode is enabled.
