Fabric OS Administrator’s Guide 301
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McDATA Fabric mode configuration restrictions 14
•Domain ID offset mode — In this mode, you can set the Domain ID Offset to any one of the
following values: 0x00, 0x20, 0x40, 0x80, 0xA0, or 0xC0. Supported Domain ID ranges are:
1-31, 33-63, 65-95, 129-159, 161-191, 193-223.
In IM 2: Once the domain ID offset is set, you only need to enter a decimal number in the 1-31
range when configuring a Domain ID in IM2. There is no need to derive the Domain ID by
subtracting the offset.
In IM 3: The Domain ID is always in the range of 1-31 plus the configured Domain ID Offset. For
example, if the configured Domain ID Offset is 0x80 (128), the Domain ID of 5 must be
configured as 133 (133 - 128 = 5).
•239 Domain_ID mode — Supports the full range of domain ID s and is available for
interopmode 3 only. This mode is only supported on the Mi10k switch and is not supported on
any of the EOSc switches. To enable 239 Domain ID Mode, specify a domain ID offset of 0xFF;
then choose any Domain ID in the 1-239 range.

Configuring the Domain_ID offset

Only the offset is configured using the interopMode command. The actual domain id is configured
using the configure command. The offset itself is always entered in hexadecimal and displayed in
hexadecimal in switch show. For instructions to convert decimal numbers to hexadecimal, refer to
Appendix E, “Hexadecimal”.
1. Connect to the switch and log in using an account assigned to the admin role.
2. Enter the interopmode --enable command for your interop mode.
3. Choose the domain ID offset for your fabric.
ATTENTION
The switch automatically sets itself online once the domain ID offset has been changed.
4. Once the domain ID offset is set, go to the configure command to set the domain ID, if
applicable. For more information on configuring the domain ID refer to Chapter 2, “Performing
Basic Configuration Tasks”.

McDATA Fabric mode configuration restrictions

The following restrictions apply to McDATA Fabric mode (interopmode 2) configurations:
•A maximum of 2048 devices can be logged in to the fabric.
•A maximum of 31 switches or domain IDs can be defined.
•Domain IDs must be in the decimal range of 1 to 31 or domain ID offset value range, on Fabric
OS switches for successful connections to M-EOS switches. The firmware automatically assigns
a valid domain ID.
NOTE
If insistent domain ID (IDID) is not enabled and a switch attempts to join the fabric with a
duplicate DID, the principal switch will assign the incoming switch a different domain ID. If the
principal switch cannot assign a different domain ID to the incoming switch, it will segment
from the fabric.
•The DCC policy or port based security is not supported in McDATA Fabric mode.