Fabric OS Administrator’s Guide 75
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Routing policies 4
Using port-based routing, you can assign a static route, in which the path chosen for traffic does
not change when a topology change occurs unless the path becomes unavailable. If the static route
violates FSPF, it is not used. In contrast, exchange-based routing policies always employ dynamic
path selection.
NOTE
For FC routers only: When an FC router is in port-based routing mode, the backbone traffic is
load-balanced based on SID and DID. When an FC router is in exchange-based routing mode, the
backbone traffic is load-balanced based on SID, DID, and OXID.
Whatever routing policy a switch is using applies to the VE_Ports as well. For more information on
VE_Ports, refer to the Fibre Channel over IP Administrator’s Guide.

AP route policy

On the Brocade 7500 switch and FR4-18i blade, eight internal physical links are used by EX_ and
VEX_Port functionality. The links are shared by both ingress and egress traffic on EX_ and
VEX_Ports. The AP (appliance) route policy dedicates some links for ingress traffic and some links
for egress traffic.
The AP Dedicated Link Policy relieves internal congestion in an environment where:
•There is a large amount of traffic going through both directions at the same time.
•There is a reduction of the effect of slow devices on the overall switch performance.
It is recommended that the default AP Shared Link Policy be used for most environments. Also, it is
recommended that you design a SAN that localizes Host to Target traffic by reducing the amount of
traffic through the router. Two additional AP policies are supported under exchange-based routing:
•AP Shared Link policy (default)
•AP Dedicated Link policy
The AP policies are independent of the routing policies. Every routing policy supports both AP
policies.
ATTENTION
Setting this policy is a disruptive process.

Routing in Virtual Fabrics

Virtual Fabrics support DPS on all partitions. DPS is limited where multiple paths are available for a
logical fabric frame entering a Virtual Fabric chassis from a base fabric that is sent out using one of
the dedicated ISLs in a logical switch.
The AP policy affecting the DPS behavior, whether it is exchange-based, device-based, or
port-based, is configured on a per logical switch basis. IOD and DLS settings are set per logical
switch as well. IOD and DLS settings for the base switch affect all traffic going over the base fabric
including any logical fabric traffic that uses the base fabric.
CAUTION
Setting the routing policy is disruptive to the fabric because it requires that you disable the switch
where the routing policy is being changed.