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Fabric OS Administrator’s Guide 299
53-1001763-02
Domain ID offset modes
14
FIGURE 50
Typical direct E_Port configuration
Domain ID offset modes
The domain ID offset in interopmode 3 (IM3) allows an M-EOS switch to operate in a fabric that
contains domain IDs other than 1-31. In interopmode 2 (IM2) the domain ID offset can only be in
the 1-31 range. In IM3, the domain ID offset only changes the range of domain IDs used, the
restriction of 31 switches in a fabric remains. You can select a domain ID offset, for example 0x00,
0x20, 0x40, 0x60, 0x80, 0xa0, or 0xc0, to allow Fabric OS switches in IM2 or IM3 to work in all of
the domain ID ranges currently supported by Fabric OS. By default, Fabric OS switches operate in
the legacy domain ID mode offset 96 (0x60).
When you change the domain ID offset, the Fabric OS switches must be offline and in the default
domain ID mode or in a domain ID offset mode with the same domain ID offset. This can be an
interopmode or an offset mode range. When switches attempt to join with a non-matching domain
ID offset, they will segment. A Fabric OS switch that is online and is joined to another fabric that
contains a switch with an out-of-range domain ID will also segment.
Using the interopMode
--
enable -mcdata/openmcdata command, configured domain ID offset
values do not change when you switch between IM2 and IM3, but the configured values behave
differently. In an IM2 fabric in legacy offset mode, the device offset is 0x60 but the domain
controller offset is 0x20. For all other domain ID offset values, the device offset is the same as the
domain controller offset. In IM3 the device offset is always the same as the domain controller
offset. The offset is used to define the minimum and maximum of the domain ID range. Refer to
Table 54 and Table 55 on page 300 for the internal representation of domain ID offset values in
IM2 and IM3 respectively.