CHAPTER
1-1
Cisco MDS 9000 Family NX-OS Interfaces Configuration Guide
OL-29284-01, Release 6.x
1
Interfaces Overview
• Trunks and PortChannels, page 1-1
• Fibre Channel Port Rate Limiting, page 1-1
• Extended Credits, page 1-2
• N Port Virtualization, page 1-2
• FlexAttach, page 1-2
Trunks and PortChannels
Trunking, also known as VSAN trunking, is a feature specific to switches in the Cisco MDS 9000
Family. Trunking enables interconnect ports to transmit and receive frames in more than one VSAN, over
the same physical link. Trunking is supported on E ports and F ports.
PortChannels aggregate multiple physical ISLs into one logical link with higher bandwidth and port
resiliency for both Fibre Channel and FICON traffic. With this feature, up to 16 expansion ports
(E-ports) or trunking E-ports (TE-ports) can be bundled into a PortChannel. ISL ports can reside on any
switching module, and they do not need a designated master port. If a port or a switching module fails,
the PortChannel continues to function properly without requiring fabric reconfiguration.
Cisco NX-OS software uses a protocol to exchange PortChannel configuration information between
adjacent switches to simplify PortChannel management, including misconfiguration detection and
autocreation of PortChannels among compatible ISLs. In the autoconfigure mode, ISLs with compatible
parameters automatically form channel groups; no manual intervention is required.
PortChannels load balance Fibre Channel traffic using a hash of source FC-ID and destination FC-ID,
and optionally the exchange ID. Load balancing using PortChannels is performed over both Fibre
Channel and FCIP links. Cisco NX-OS software also can be configured to load balance across multiple
same-cost FSPF routes.
Fibre Channel Port Rate Limiting
The Fibre Channel port rate-limiting feature for the Cisco MDS 9100 Series controls the amount of
bandwidth available to individual Fibre Channel ports within groups of four host-optimized ports.
Limiting bandwidth on one or more Fibre Channel ports allows the other ports in the group to receive a
greater share of the available bandwidth under high-utilization conditions. Port rate limiting is also
beneficial for throttling WAN traffic at the source to help eliminate excessive buffering in Fibre Channel
and IP data network devices.
