> # Trunk-Allowed VSAN Lists and VF_IDs

> Each Fibre Channel interface has an associated trunk-allowed VSAN list. In TE-port mode, frames are transmitted and received in one or more VSANs specified in this list. By default, the VSAN range (1 through 4093) is included in the trunk-allowed list.

> The common set of VSANs that are configured and active in the switch are included in the trunk-allowed VSAN list for an interface, and they are called allowed-active VSANs. The trunking protocol uses the list of allowed-active VSANs at the two ends of an ISL to determine the list of operational VSANs in which traffic is allowed.

> Switch 1 has VSANs 1 through 5, switch 2 has VSANs 1 through 3, and switch 3 has VSANs 1, 2, 4, and 5 with a default configuration of trunk-allowed VSANs. All VSANs configured in all three switches are allowed-active. However, only the common set of allowed-active VSANs at the ends of the ISL become operational.

> For all F, N, and NP ports, the default VF_ID is 1 when there is no VF_ID configured. The trunk-allowed VF_ID list on a port is same as the list of trunk-allowed VSANs. VF_ID 4094 is called the control VF_ID and it is used to define the list of trunk-allowed VF-IDs when trunking is enabled on the link.

> If F port trunking and channeling is enabled, or if switchport trunk mode on is configured in NPV mode for any interface, or if NP PortChannel is configured, the VSAN and VF-ID ranges available for the configuration are as described in Table 9-3.

> Table 9-3 VSAN and VF-ID Reservations
> VSAN or VF-ID | Description
> --- | ---
> 000h | Cannot be used as virtual fabric identifier.
> 001h(1) to EFFh(3839) | This VSAN range is available for user configuration.
> F00h(3840) to FEEh(4078) | Reserved VSANs and they are not available for user configuration.
> FEFh(4079) | EVFP isolated VSAN.
> FF0h(4080) to FFEh(4094) | Used for vendor-specific VSANs.
> FFFh | Cannot be used as virtual fabric identifier.

> Note If the VF_ID of the F port and the N port do not match, then no tagged frames can be exchanged.

> You can configure a select set of VSANs (from the allowed-active list) to control access to the VSANs specified in a trunking ISL.

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