HP StorageWorks 2/16V HP StorageWorks Fabric OS 5.2.x administrator guide (569 - Page 206

Fibre Channel NAT and phantom domains Within an edge fabric or across a backbone fabric, the standard Fibre Channel FSPF protocol determines how frames are routed from the source Fibre Channel (FC) device to the destination FC device. The source or destination device can be a proxy device. When frames traverse the fabric through a 400 MP Router or 4/256 SAN Director in the backbone (BB), the frames are routed to another EX_Port or VEX_Port. Fibre Channel fabrics require that all ports (EX_Ports or VEX_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 might be duplicated within another fabric, just as IP addresses 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 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 different PIDs than the real devices that they represent, allowing the proxy devices to have appropriate PIDs for the address space of their corresponding fabric. All EX_Ports connected to same edge fabric from one physical FC router present a single front phantom domain and one additional translate (xlate) phantom domain for each edge fabric accessed through it. All EX_Ports and 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. Xlate domains are presented as being connected topologically behind one or more front domains; each FC-Router presents one front domain to edge fabric. This allows redundant paths to remote fabrics to present redundant paths to proxy devices to an edge fabric. Phantom domains are like logical switches that appear to be connected to an edge fabric through the front domains that are presented by EX_Ports and/or VEX_Ports. 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 BB. The BB xlate domains are topologically connected to FC routers and participate in FC-Protocol in BB. Front domains are not needed in the BB. As in the case of xlate domain in edge fabric, BB xlate domains provide additional bandwidth and redundancy by being able to present itself being connected to single or multiple FC routers with each FC router capable of connecting multiple IFLs to edge fabrics. Setting up the FC-FC routing service To set up the FC-FC Routing Service, perform the following tasks: 1. "Performing verification checks" next 2. "Assigning Backbone Fabric IDs" on page 111- 3 3. "Configuring FCIP tunnels (optional)" on page -209 4. "Configuring FC-FC routing to work with Secure Fabric OS (optional)" on page -209 5. "Configuring an interfabric link" on page -211 6. "FC router port cost (optional)" on page -219 7. "EX_Port frame trunking (optional)" on page -222 8. "Configuring LSANs and zoning" on page -216 See "Configuring Directors" on page 207 for more details about configuration options. 206 Using the FC-FC routing service