Dell EMC SmartFabric OS10 User Guide Release 10.5.0

Pinning FCoE traffic to a specific port of a port-channel

You can isolate FIP and FCoE traffic by configuring a pinned port at the FCoE LAG.

FCoE LAG is the port-channel used for FIP and FCoE traffic in the intermediate switches between server and storage devices.

VLT provides Active/Active LAN connectivity on converged links by forwarding traffic in multiple paths to multiple upstream devices without STP blocking any of the uplinks. This works for Ethernet traffic, but FCoE requires dedicated links for each SAN Fabric. FCoE traffic sent on VLT breaks SAN fabric isolation.

The FC sessions form between FC nodes and FCoE sessions happen between Ethernet nodes.

To form FC or FCoE sessions, the fabric login request and reply must traverse the switch through the same port. The fabric login request initiated from the server through the switch reaches the SAN Fabric. The login accept response is hashed out to any of the ports in the port-channel. If the server receives the response on a different port than where the request was sent, the server keeps retrying the request. Because of this action, the FC or FCoE sessions learnt based on the login accept response change to the unstable state. The sessions keep flapping until the request and response converge in the same port. To avoid this, pin one of the ports in the port-channel.

To support FCoE on multi-level VLT networks, use port pinning in FCoE LAGs. Port pinning is a static configuration that restricts the FIP and FCoE traffic to one port of the port-channel overriding hardware LAG hashing. The system classifies and redirects the packets exchanged during FCoE sessions to the port based on the ACL configuration. The remaining Ethernet traffic flows through both the pinned port and other ports in the port-channel, based on LAG hashing. Dell EMC recommends to use pinned port if there are more than one port in FCoE LAG. In a VLT network, the server has two unique FCoE sessions to SAN fabric and the traffic flows based on pinned port configuration. If there is only one port in the port-channel, there is no need for a pinned port.

Limitations:

• The system uses an ACL table for ENode MAC with a redirect port option similar to FCF. This limits the number of FC or FCoE sessions.
• When the pinned port goes down, you must manually re-configure another active port in the port-channel as pinned port. You can perform this re-configuration only in the intermediate switches, but not in the server.
• If there is a mismatch in the configuration or if the pinned port goes down, the system does not use other ports in port-channel even if there is a valid path to server and storage device.
• When you add or remove a pinned port when FCoE sessions are active, the system clears and re-initiates the FCoE sessions based on the configuration. The system displays warning messages during the configuration.

The following illustrations show VLT and non-VLT networks with FCoE traffic flowing through pinned port.