Fabric OS Administrator's Guide v7.0.0 (53-1002148-02, June 2011)

Fabric OS Administrator’s Guide 469
53-1002148-02
Fibre Channel routing concepts
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Figure 79 shows a phantom topology for the physical topology shown in Figure 78. In this figure,
the dashed lines and shapes represent the phantom topology from the perspective of Fabric 1.
Fabrics 2 and 3 also see phantom topologies, but they are not shown in this example. In this figure,
note the following:
• Front domain 1 and Front domain 2 are front domains for EX_Ports connecting to Fabric 1.
There is one front domain for each FC router that is connected to Fabric 1.
• Xlate domain 1 and Xlate domain 2 represent Fabrics 2 and 3, respectively. No xlate domain is
created for Fabric 4 because there are no LSAN devices in Fabric 4.
• Target 1’, Target 2’, and Target 3’ are proxy devices for Target 1, Target 2, and Target 3,
respectively.
FIGURE 79 EX_Port phantom switch topology
All EX_Ports or VEX_Ports connected to an edge fabric use the same xlate domain ID for an
imported edge fabric; this value persists across switch reboots and fabric reconfigurations.
If you lose connectivity to the edge fabric because of link failures or the IFL being disabled, xlate
domains remain visible. This prevents unnecessary fabric disruptions caused by xlate domains
repeatedly going offline and online due to corresponding IFL failures. To remove the xlate domain
from the backbone, see “Identifying and deleting stale xlate domains.”
The combination of front domains and xlate domains allows routing around path failures, including
path failures through the routers. The multiple paths to an xlate domain provide additional
bandwidth and redundancy.
There are some differences in how the xlate domain is presented in the backbone fabric. The
backbone xlate domains are topologically connected to FC routers and participate in FC-FC routing
protocol in the backbone fabric. Front domains are not needed in the backbone fabric. As in the
case of an xlate domain in an edge fabric, backbone fabric xlate domains provide additional
bandwidth and redundancy by being able to present themselves as connected to single or multiple
FC routers with each FC router capable of connecting multiple IFLs to edge fabrics.
Fabric 1
Target 1' Target 3'Target 2'
Front domain 1
(FC router 1)
Front domain 2
(FC router 2)
Xlate domain 1
(Fabric 2)
Xlate domain 2
(Fabric 3)
Host 1