HP StorageWorks 8/80 HP StorageWorks Fabric OS 6.2 administrator guide (5697-0 - Page 376

Host 1 Fabric 1 Front domain 1 (FC router 1) Xlate domain 1 (Fabric 2) Front domain 2 (FC router 2) Xlate domain 2 (Fabric 3) Target 1' Target 2' Target 3' Figure 64 EX_Port phantom switch topology All EX_Ports or VEX_Ports connected to an edge fabric use the same xlate domain ID number 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, disable all EX_Ports or VEX_Ports through which the xlate domain was created. 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. Use the fcrXlateConfig command to display or assign a preferred domain ID to a translate domain or, in some scenarios, to prevent the creation of an unnecessary xlate domain. See the Fabric OS Command Reference for more details about this command. Fibre Channel Network Address Translation 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 (DIDs) 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 374 Using the FC-FC routing service