Fip Virtual Link Instantiation; Fcoe Frame Format; Vlan Tagging For Fcoe Frames - Cisco Nexus 7000 series Configuration Manual

FCoE and FIP
• Cisco Nexus 7000
• Cisco MDS 9500

FIP Virtual Link Instantiation

FIP is used to perform device discovery, initialization, and link maintenance. FIP performs the following
tasks:
• FIP VLAN discovery— Discovers the FCoE VLAN that will be used by all other FIP protocols as well
as by the FCoE encapsulation for Fibre Channel payloads on the established virtual link. FIP VLAN
discovery occurs in the native VLAN used by the initiator or target to exchange Ethernet traffic. The
FIP VLAN discovery protocol is the only FIP protocol running on the native VLAN; all other FIP
protocols run on the discovered FCoE VLANs.
• FIP FCF discovery—When a FCoE device is connected to the fabric, it sends a Discovery Solicitation
message. A Fibre Channel Forwarder (FCF) or a switch responds to the message with a Solicited
Advertisement that provides an FCF MAC address to use for subsequent logins.
• FCoE virtual link instantiation— FIP defines the encapsulation of fabric login (FLOGI), fabric discovery
(FDISC), logout (LOGO), and exchange link parameter (ELP) frames along with the corresponding
reply frames. The FCoE devices use these messages to perform a fabric login.
• FCoE virtual link maintenance— FIP periodically sends maintenance messages between the switch and
the CNA to ensure that the connection is still valid.

FCoE Frame Format

FCoE is implemented when the switch encapsulates a Fibre Channel frame in an Ethernet packet with a
dedicated Ethernet type, 0x8906. The packet has a 4-bit version field. The other header fields in the frame
(the source and destination MAC addresses, VLAN tags, and frame markers) are all standard Ethernet fields.
Reserved bits pad the FCoE frame to the IEEE 802.3 minimum packet length of 64 bytes.
A Fibre Channel frame consists of 36 bytes of headers and up to 2112 bytes of data for a total maximum size
of 2148 bytes. The encapsulated Fibre Channel frame has all the standard headers, which allow it to be passed
to the storage network without further modification. To accommodate the maximum Fibre Channel frame in
an FCoE frame, the class-fcoe is defined with a default Maximum Transmission Unit (MTU) of 2240 bytes.

VLAN Tagging for FCoE Frames

The Ethernet frames that are sent by the switch to the adapter include the IEEE 802.1Q tag. This tag includes
a field for the class of service (CoS) value used by the priority flow control (PFC). The IEEE 802.1Q tag also
includes a VLAN field.
The switch expects frames from a FIP T11-compliant CNA to be tagged with the VLAN tag for the FCoE
VLAN. Frames that are not correctly tagged are discarded.
Note You cannot map VLAN 1 or the native VLAN to an FCoE VSAN.
The following switches do not support Pre-FIP on Generation 1 CNAs:
Cisco NX-OS FCoE Configuration Guide for Nexus 7000 and MDS 9500
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FCoE
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