Send feedback to nx5000-docfeedback@cisco.com
1-7
Cisco Nexus 5000 Series Switch CLI Software Configuration Guide
OL-16597-01
Chapter 1      Configuring Fibre Channel Interfaces
Information About Fibre Channel Interfaces
Buffer-to-Buffer Credits
Buffer-to-buffer credits (BB_credits) are a flow-control mechanism to ensure that Fibre Channel 
interfaces do not drop frames. BB_credits are negotiated on a per-hop basis.
In Cisco Nexus 5000 Series switches, the BB_credit mechanism is used on Fibre Channel interfaces but 
not on virtual Fibre Channel interfaces. Virtual Fibre Channel interfaces provide flow control based on 
capabilities of the underlying physical Ethernet interface. 
Isolation due to ELP failure The port negotiation failed. Only E ports 
and TE ports 
Isolation due to ESC failure The port negotiation failed.
Isolation due to domain 
overlap
The Fibre Channel domains (fcdomain) overlap.
Isolation due to domain ID 
assignment failure
The assigned domain ID is not valid.
Isolation due to the other side 
of the link E port isolated
The E port at the other end of the link is isolated.
Isolation due to invalid fabric 
reconfiguration
The port is isolated due to fabric reconfiguration.
Isolation due to domain 
manager disabled
The fcdomain feature is disabled.
Isolation due to zone merge 
failure
The zone merge operation failed.
Isolation due to VSAN 
mismatch
The VSANs at both ends of an ISL are different.
port channel administratively 
down
The interfaces belonging to the SAN port channel are 
down.
Only SAN 
port channel 
interfaces
Suspended due to incompatible 
speed
The interfaces belonging to the SAN port channel have 
incompatible speeds.
Suspended due to incompatible 
mode
The interfaces belonging to the SAN port channel have 
incompatible modes.
Suspended due to incompatible 
remote switch WWN
An improper connection is detected. All interfaces in a 
SAN port channel must be connected to the same pair 
of switches.
Bound physical interface down The Ethernet interface bound to a virtual Fibre Channel 
interface is not operational.
Only virtual 
Fibre 
Channel 
interfaces
STP not forwarding in FCoE 
mapped VLAN
The Ethernet interface bound to a virtual Fibre Channel 
interface is not in an STP forwarding state for the 
VLAN associated with the virtual Fibre Channel 
interface
Only virtual 
Fibre 
Channel 
interfaces
Table 1-4 Reason Codes for Nonoperational States (continued)
Reason Code (long version) Description
Applicable 
Modes