Troubleshooting A Domain Id Conflict - Cisco MDS 9000 Series Troubleshooting Manual

Chapter 3 Troubleshooting Switch Level Issues and Interswitch Connectivity
S e n d c o m m e n t s t o m d s f e e d b a c k - d o c @ c i s c o . c o m .

Troubleshooting a Domain ID Conflict

In a Fibre Channel network, the principal switch is used to issue 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 pre-existing switches becomes that principal switch. The election of the
new principal switch is characterized by the following rules:
1.
2.
3.
When merging two fabrics, the administrator can expect the following behavior:
•
•
•
•
There are several reasons why two switch fabrics would not merge:
•
In this case, the following error message is returned in the show interface command.
switch# show interface fc2/14
fc2/14 is down (Isolation due to domain overlap)
To view which domain are currently in your fabric use the following command. This command can be
issued to both fabrics to determine which domain IDs are overlapping.
OL-5183-02, Cisco MDS SAN-OS Release 1.3
A switch with a non-empty domain ID list has priority over a switch that has an empty domain ID
list, and the principal switch will be the principal switch of the first fabric. In the case of a single
switch fabric, it does not contain a domain ID list.
If both fabrics have a domain ID list, the priority between the two principal switches is determined
by configured switch priority. This is a user-settable parameter - the lower the value the higher the
priority.
If the principal switch cannot be determined by the two previous criteria, the principal switch is then
determined by the World Wide Names of the two switches. The lower value has the higher priority.
When connecting a single-switch fabric to a multi-switch fabric, the multi-switch fabric always
retains its principal switch regardless of the principal switch priority setting on the single switch
fabric.
When powering up a new switch that is connected to an existing fabric with two or more switches,
the existing switch fabric always retains its principal switch, even if the new switch has a higher
administratively assigned principal switch priority.
When powering up a new switch that is connected to a standalone switch, the new principal switch
is determined by the administratively set priority. If no priority is set (the default priority is used in
every switch), it is determined by the World Wide Name. This also applies to connecting to two
single-switch fabrics.
When connecting a multi-switch fabric to another multi-switch fabric, the principal switch is
determined by the administratively set priority. If no priority is set (default value is used by every
switch) it is determined by the World Wide Name of the existing principal switches of the two
fabrics.
If two switch fabrics with two or more switches are connected, and both fabrics that have switches
with the domain ID already assigned and the auto-reconfigure option is disabled (this option is
disabled by default), the E ports that are used to connect the two fabrics will be isolated.
Hardware is Fibre Channel, WWN is 20:4e:00:05:30:00:63:9e
vsan is 2
Beacon is turned off
192 frames input, 3986 bytes, 0 discards
0 runts, 0 jabber, 0 too long, 0 too short
0 input errors, 0 CRC, 3 invalid transmission words
0 address id, 0 delimiter
0 EOF abort, 0 fragmented, 0 unknown class
231 frames output, 3709 bytes, 16777216 discards
Received 28 OLS, 19 LRR, 16 NOS, 48 loop inits
Transmitted 62 OLS, 22 LRR, 25 NOS, 30 loop inits
Troubleshooting E Port Connectivity - ISL Isolation
Cisco MDS 9000 Family Troubleshooting Guide
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