Brocade Fabric OS Administrators Guide (Supporting Fabric OS v7.3.0) - Manual (Page 540)

FC-FC routing topologies
The FC-FC routing service provides two types of routing:
• Edge-to-edge
Occurs when devices in one edge fabric communicate with devices in another edge fabric through
one or more FC routers.
• Backbone-to-edge
Occurs when FC routers connect to a common fabric--known as a backbone fabric --through
E_Ports.
A backbone fabric can be used as a transport fabric that interconnects edge fabrics. FC routers also
enable hosts and targets in edge fabrics to communicate with devices in the backbone fabric, known
as backbone-to-edge routing . From the perspective of the edge fabric, the backbone fabric is like any
other edge fabric. For the edge fabric and backbone fabric devices to communicate, the shared
devices must be presented to each other's native fabric.
To do so, at least one translate phantom domain is created in the backbone fabric. This translate
phantom domain represents the entire edge fabric. The shared physical devices in the edge have
corresponding proxy devices on the translate phantom domain.
Each edge fabric has one and only one translate phantom domain to the backbone fabric. The
backbone fabric device communicates with the proxy devices whenever it needs to contact the shared
physical devices in the edge. The FC-FC routing service receives the frames from the backbone
switches destined to the proxy devices, and redirects the frames to the actual physical devices. When
connected to edge fabrics, the translate phantom domain can never be the principal switch of the
backbone fabric. Front domains are not created; rather, only translate phantom domains are created in
the backbone fabric.
Devices are exported from the backbone fabric to one or more edge fabrics using LSANs. Refer to
LSAN zone configuration on page 559 for more information.
Phantom domains
A phantom domain is a domain created by the Fibre Channel router. The FC router creates two types
of phantom domains: front phantom domains and translate phantom domains.
A front phantom domain, or front domain, is a domain that is projected from the FC router to the edge
fabric. There is one front phantom domain from each FC router to an edge fabric, regardless of the
number of EX_Ports connected from that router to the edge fabric. Another FC router connected to the
same edge fabric projects a different front phantom domain.
A translate phantom domain, also referred to as translate domain or xlate domain, is a router virtual
domain that represents an entire fabric. The EX_Ports present xlate domains in edge fabrics as being
topologically behind the front domains; if the xlate domain is in a backbone fabric, then it is
topologically present behind the FC router because there is no front domain in a backbone fabric.
If an FC router is attached to an edge fabric using an EX_Port, it creates xlate domains in the fabric
corresponding to the imported edge fabrics with active LSANs defined. If you import devices into the
backbone fabric, then an xlate domain is created in the backbone device in addition to the one in the
edge fabric.
Figure 86 shows a sample physical topology. This figure shows four FC routers in a backbone fabric
and four edge fabrics connected to the FC routers.
FC-FC routing topologies
540 Fabric OS Administrators Guide
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