Brocade Fabric OS Administrator's Guide Supporting Fabric OS v6.3.0 (53-1001336-02, November 2009)

Fabric OS Administrator’s Guide 61
53-1001336-02
Routing policies
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Fibre Channel NAT
Within an edge fabric or across a backbone fabric, the standard Fibre Channel fabric shortest path
first (FSPF) protocol determines how frames are routed from the source Fibre Channel device to the
destination FC device. The source or destination device can be a proxy device.
Fibre Channel fabrics require that all ports be identified by a unique PID. In a single fabric, FC
protocol guarantees that domain IDs are unique, and so a PID formed by a domain ID and area ID is
unique within a fabric. However, the domain IDs and PIDs in one fabric may be duplicated within
another fabric, just as IP addresses that are unique to one private network are likely to be
duplicated within another private network.
In an IP network, a network router can maintain network address translation (NAT) tables to replace
private network addresses with public addresses when a packet is routed out of the private
network, and to replace public addresses with private addresses when a packet is routed from the
public network to the private network. The Fibre Channel routing equivalent to this IP-NAT is the
Fibre Channel network address translation (FC-NAT). Using FC-NAT, the proxy devices in a fabric can
have PIDs that are different from the real devices they represent, allowing the proxy devices to have
appropriate PIDs for the address space of their corresponding fabric.
Routing policies
By default, all routing protocols place their routes into a routing table. You can control the routes
that a protocol places into each table and the routes from that table that the protocol advertises by
defining one or more routing policies and then applying them to the specific routing protocol.
The routing policy is responsible for selecting a route based on one of two user-selected routing
policies:
• Port-based routing
• Exchange-based routing
On the Brocade 300, 4100, 4900, 5000, 5410, 5424, 5450, 5460, 5470, 5480, 5100, 5300,
5424, 7500, 7500E, 7600, 7800 and 8000 switches, the Brocade 48000 director, and the
Brocade DCX and DCX-4S enterprise-class platforms (all 4 Gbps ASICs and later) routing is handled
by the FSPF protocol and either the port-based routing or exchange-based routing policies.
Each switch can have its own routing policy and different policies can exist in the same fabric.
ATTENTION
For most configurations, the default routing policy is optimal and provides the best performance. You
should change the routing policy only if there is a performance issue that is of concern, or if a
particular fabric configuration requires it.
Displaying the current routing policy
1. Connect to the switch and log in as admin.
2. Enter the aptPolicy command with no parameters.
The current policy is displayed, followed by the supported policies for the switch.