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29-5
Cisco MDS 9000 Family Fabric Manager Configuration Guide
OL-17256-03, Cisco MDS NX-OS Release 4.x
Chapter 29 Configuring Inter-VSAN Routing
Inter-VSAN Routing
IVR NAT
Without Network Address Translation (NAT), IVR requires unique domain IDs for all switches in the
fabric. You can enable IVR NAT to allow non-unique domain IDs. This feature simplifies the deployment
of IVR in an existing fabric where non-unique domain IDs might be present.
To use IVR NAT, it must be enabled in all IVR-enabled switches in the fabric IVR configuration
distribution . By default, IVR NAT and IVR configuration distribution are disabled in all switches in the
Cisco MDS 9000 Family.
IVR NAT Requirements and Guidelines
Following are requirements and guidelines for using IVR NAT:
• IVR NAT port login (PLOGI) requests received from hosts are delayed a few seconds to perform the
rewrite on the FC ID address. If the host's PLOGI timeout value is set to a value less than five
seconds, it may result in the PLOGI being unnecessarily aborted and the host being unable to access
the target. We recommend that you configure the host bus adapter for a timeout of at least ten
seconds (most HBAs default to a value of 10 or 20 seconds).
Note IVR NAT requires Cisco MDS SAN-OS Release 2.1(1a) or later on all switches in the fabric performing
IVR. If you have isolated switches with an earlier release that are involved in IVR, you must remove any
isolated fabrics from monitoring by Fabric Manager server and then re-open the fabric to use IVR NAT.
See the “Selecting a Fabric to Manage Continuously” section on page 3-3.
• Load balancing of IVR NAT traffic across equal cost paths from an IVR-enabled switch is not
supported. However, load balancing of IVR NAT traffic over PortChannel links is supported. The
load balancing algorithm for IVR NAT traffic over port-channel with Generation 1 linecards is
SRC/DST only. Generation 2 linecards support SRC/DST/OXID based load balancing of IVR NAT
traffic across a port-channel.
• You cannot configure IVR NAT and preferred Fibre Channel routes on Generation 1 module
interfaces.
IVR NAT allows you to set up IVR in a fabric without needing unique domain IDs on every switch in
the IVR path. IVR NAT virtualizes the switches in other VSANs by using local VSAN for the destination
IDs in the Fibre Channel headers. In some Extended Link Service message types, the destinations IDs
are part of the payload. In these cases, IVR NAT replaces the actual destination ID with the virtualized
destination ID. IVR NAT supports destination ID replacement in the Extended Link Service messages
described in Table 29-2.
Table 29-2 Extended Link Service Messages Supported by IVR NAT
Extended Link Service Messages
Link Service Command
(LS_COMMAND) Mnemonic
Abort Exchange 0x06 00 00 00 ABTX
Discover Address 0x52 00 00 00 ADISC
Discover Address Accept 0x02 00 00 00 ADISC ACC
Fibre Channel Address Resolution Protocol
Reply
0x55 00 00 00 FARP-REPLY
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