Brocade Access Gateway Administrator's Guide (Supporting Fabric OS v7.3.0) - Manual (Page 43)

Mapping priority
To avoid potential problems when both port and device mapping are implemented, AG uses the
following priority system when verifying policies to select the N_Port where a fabric login (FLOGI) is
routed. Access Gateway considers all available mappings in the following order until one can be used.
NOTE
Only NPIV devices can use device mapping and the automatic Device Load Balancing policy. Device
Load Balancing policy is enabled per module rather than per port group.
For more information, refer to Port Grouping policy on page 52.
1. Static device mapping to N_Port (if defined)
2. Device mapping to N_Port group (if defined)
3. Automatic Device Load Balancing within a port group (if enabled)
4. Port mapping to an N_Port
5. Port mapping to an N_Port in a port group (if defined)
Device mapping considerations
Consider the following points when using device mapping:
• If the N_Port is disabled, all devices that are mapped to it will be disabled. Depending on the
effective failover policy, the devices will be enabled on other N_Ports.
• Similar to port mappings, device mappings are affected by changes to underlying F_Ports. In other
words, if an F_Port needs to be taken offline, both the physical device and all virtual nodes behind
it will momentarily go offline.
• Once devices are mapped to an N_Port rather than an N_Port group, they cannot be automatically
rebalanced to another N_Port if an additional N_Port comes online.
• There can be cases where two NPIV devices logging in through the same F_Port are mapped to
two different N_Ports that are connected to two different fabrics. In this case, both NPIV devices
may be allocated the same PID by their respective fabrics. Once Access Gateway detects this
condition, it will disable that F_Port, and the event will be logged.
NOTE
Access Gateway algorithms reduce the chances of PID collisions, but they cannot be totally eliminated.
In some cases, you may be able to configure your virtual or physical fabrics to further reduce PID
collisions.
• Device mapping is not supported when firmware is downgraded to Fabric OS v6.3.x or earlier. You
must delete device mappings before downgrading or disable Device Load Balancing.
• Static and dynamic device mapping are only supported on the edge module in a cascaded Access
Gateway configuration.
• When mapping devices to a port group, make sure that all ports in the group have the same NPIV
login limit. If some ports have a lower login limit than the other ports, and there are many logins to
the group, some devices will repeatedly attempt to connect to the device with the lower limit
(because it has the fewest logins) and fail to connect.
Mapping priority
Access Gateway Administrator's Guide 41
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