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FC Services
S e n d d o c u m e n t c o m m e n t s t o n e x u s 5 k - d o c f e e d b a c k @ c i s c o . c o m .
Interface is isolated because of FC Domain ID overlap
The Fibre Channel or SAN port channel interface of a Cisco Nexus 5000 switch (in fabric mode) that is
connected to an FC switch with the xE port type is isolated because of a domain overlap. The following
example shows possible logging messages in the show logging command log:
Example:
PORT-5-IF_DOWN_DOMAIN_OVERLAP_ISOLATION: Interface fc <slot/port> is down (Isolation due
to domain overlap).
%FCDOMAIN-2-EPORT_ISOLATED: %$VSAN <vsan-id>%$ Isolation of interface san-port-channel
<channel-id> (reason: domain ID assignment failure)
%FCDOMAIN-2-EPORT_ISOLATED: %$VSAN <vsan-id>%$ Isolation of interface san-port-channel
<channel-id> (reason: other side Eport indicates isolation)
Possible Cause
Two switch fabrics might not merge. If two fabrics with two or more switches are connected, have at
least one assigned domain ID in common, and the auto-reconfigure option is disabled (this option is
disabled by default), then the E ports that are used to connect the two fabrics will be isolated due to
domain ID overlap.
In a Fibre Channel network, the principal switch assigns domain IDs when a new switch is added to an
existing fabric. However, when two fabrics merge, the principal switch selection process determines
which one of the preexisting switches becomes the principal switch for the merged fabric.
The election of the new principal switch is characterized by the following rules:
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•
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Solution
To resolve an FC domain ID overlap, you can change the overlapping static domain ID by manually
configuring a new static domain ID for the isolated switch, or disable the static domain assignment and
allow the switch to request a new domain ID after a fabric reconfiguration.
To assign a static domain ID using the NX-OS CLI
All devices attached to the switch in the VSAN get a new FC ID when a new domain ID is assigned.
Some hosts or storage devices may not function as expected if the FC ID of the host or storage device
changes.
To verify FC domain ID overlap and reassign a new domain ID using the CLI, perform the following
steps:
Step 1
Enter the show interface fc <slot/port> command to view the isolation error message for the E port.
Example:
switch(config)# show int fc 2/2
fc2/2 is down (Isolation due to domain other side eport isolated)
Cisco Nexus 5000 Series Troubleshooting Guide
5-28
A switch with a populated domain ID list takes priority over a switch that has an empty domain ID
list. The principal switch becomes the one in the fabric with the populated domain ID list.
If both fabrics have a domain ID list, the priority between the two principal switches is determined
by the configured switch priority. This is a parameter that can be set by the user. The lower the value
of the parameter, the higher the priority.
If the principal switch cannot be determined by the two previous criteria, the principal switch is then
determined by the WWNs of the two switches. The lower the value of the WWN, the higher the
switch priority.
Hardware is Fibre Channel, SFP is short wave laser w/o OFC (SN)
Port WWN is 20:42:00:0d:ec:d5:fe:00
Chapter 5
Troubleshooting SAN Switching Issues
OL-25300-01
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