The CNAs that are connected to a switch are programmed to accept the configuration values that are sent by
the switch, allowing the switch to distribute configuration values to all attached CNAs, which reduces the
possibility of configuration errors and simplifies CNA administration.
Lossless Ethernet
Standard Ethernet is a best-effort medium which means that it lacks any form of flow control. In the event of
congestion or collisions, Ethernet drops packets. The higher level protocols detect the missing data and
retransmit the dropped packets.
To properly support Fibre Channel, Ethernet has been enhanced with a priority flow control (PFC) mechanism.
Logical Link Up/Down
On a native Fibre Channel link, some configuration actions (such as changing the VSAN) require that you
reset the interface status. When you reset the interface status, the switch disables the interface and then
immediately reenables the interface.
Caution:
If an Ethernet link provides FCoE service, do not reset the physical link because this action is disruptive to
all traffic on the link.
The logical link up/down feature allows the switch to reset an individual virtual link. The logical link down
is signaled with a FIP Clear Virtual Link message.
Caution:
If the CNA does not support the logical link level up/down feature, the CNA resets the physical link, which
means that all traffic on the Ethernet interface is disrupted.
Converged Network Adapters
Cisco NX-OS switches support the following CNA types:
•
Hardware adapter
◦
Works with the existing Fibre Channel host bus adapter (HBA) driver and Ethernet Network
Interface Card (NIC) driver in the server.
◦
Server operating system view of the network is unchanged; the CNA presents a SAN interface and
a LAN interface to the operating system.
•
FCoE software stack
◦
Runs on existing 10-Gigabit Ethernet adapters.
The following Cisco NX-OS series and platforms support Generation 2 CNAs that use the FIP to exchange
information about its available capabilities and to negotiate the configurable values with the switch:
•
Cisco Nexus 2232
•
Cisco Nexus 5000
•
Cisco Nexus 5500
Cisco NX-OS FCoE Configuration Guide for Nexus 7000 and MDS 9500
6
OL-25809-02
FCoE
Lossless Ethernet
