> # World Wide Names

> The world wide name (WWN) in the switch is equivalent to the Ethernet MAC address. As with the MAC address, you must uniquely associate the WWN to a single device. The principal switch selection and the allocation of domain IDs rely on the WWN. The WWN manager, a process-level manager residing on the switch’s supervisor module, assigns WWNs to each switch.

> Cisco MDS 9000 Family switches support three network address authority (NAA) address formats (see Table 28-1).

> Table 28-1 Standardized NAA WWN Formats
> NAA Address | NAA Type | WWN Format
> --- | --- | ---
> IEEE 48-bit address | Type 1 = 0001b | 000 0000 0000b | 48-bit MAC address
> IEEE extended | Type 2 = 0010b | Locally assigned | 48-bit MAC address
> IEEE registered | Type 5 = 0101b | IEEE company ID: 24 bits | VSID: 36 bits

> Caution | Changes to the world-wide names should be made by an administrator or individual who is completely familiar with switch operations.

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