Brocade Network OS Administrator’s Guide v4.1.1 - Manual (Page 340)

original MAC header is now transformed as follows: the DA is changed from VF1 to FCF-C and the
SA is changed from VN1 to FCF-A. This occurs at point 2 in the previous figure.
6. The frame gets a Transparent Interconnection of Lots of Links (TRILL) header and traverses across
the fabric to reach FCF-C. The TRILL header indicates that the source is RBridge 1 and the
destination is RBridge 3. This occurs at point 2 in the previous figure.
7. The outer MAC header is a link level header that gets the frame from FCF-A to FCF-B. FCF-B
receives the frame. FCF-B scans the TRILL header, decodes the destination RBridge ID in the
frame, and forwards the frame. FCF-B only modifies the Layer 2 header. It neither looks up nor
modifies anything in the FC header or the inner MAC header. This occurs at point 3 in the previous
figure.
8. FCF-C receives the frame. FCF-C scans the TRILL header and decodes the destination RBridge
ID. FCF-C promotes the frame to Layer 3 lookup, because the FCF-C is the DA in the inner MAC
header. FCF-C then scans the FC header and does something similar to an area route lookup in FC
SAN. This lookup yields the MAC address of VN2 and the VF interface (in this case, VF2)
information that it needs to use to forward the frame to VN2. This is occurs at point 4 in the previous
figure.
9. VN2 receives the PLOGI. The PLOGI response from VN2 traverses back to VN1 in similar fashion.
NOTE
It is assumed that both VN1 and VN2 are configured to be in the same FCoE VLAN, and FCoE
forwarding is enabled on this VLAN in the Brocade VCS Fabric. Network OS v4.0.0 and later
supports only one FCoE VLAN for all FCoE devices connected to the fabric.
FCoE and Layer 2 Ethernet
The Brocade VDX hardware contains DCB ports that support FCoE forwarding. The DCB ports are
also backwards-compatible and support classic Layer 2 Ethernet networks (as shown in the figure
below). In Layer 2 Ethernet operation, a host with a Converged Network Adapter (CNA) can be directly
attached to a DCB port on the Brocade VDX hardware. Another host with a classic 10-gigabit Ethernet
network interface card (NIC) can be either directly attached to a DCB port, or attached to a classic
Layer 2 Ethernet network that is attached to the Brocade VDX hardware.
FCoE and Layer 2 Ethernet
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