SAN port channels refer to the aggregation of multiple physical interfaces into one logical interface to provide higher aggregated bandwidth, load balancing, and link redundancy. Port channels can connect to interfaces across switching modules, so a failure of a switching module cannot bring down the port channel link.
In Figure 8-28, port channel A aggregates two links on two interfaces on the same switching module at each end of a connection. Port channel B also aggregates two links, but each link is connected to a different switching module. If the switching module goes down, traffic is not affected.
Figure 8-28 Port Channel Flexibility
Types of SAN Port Channels
An E port channel provides a point-to-point connection over ISL (E ports) or EISL (TE ports), as shown in Figure 8-29. Multiple links can be combined into a port channel, and it increases the aggregate bandwidth on an ISL by distributing traffic among all functional links in the channel. It load balances across multiple links and maintains optimum bandwidth utilization. Load balancing is based on the source ID, destination ID, and exchange ID (OX ID). The E port channel provides high availability on an ISL. If one link fails, traffic previously carried on this link is switched to the remaining links. If a link goes down in a port channel, the upper protocol is not aware of it. To the upper protocol, the link is still there, although the bandwidth is diminished. The routing tables are not affected by link failure. Port channels may contain up to 16 physical links and may span multiple modules for added high availability. Trunking enables a link transmitting frames in the EISL format to carry (trunk) multiple VSAN traffic.
Figure 8-29 Port Channel and Trunking
An F port channel is also a logical interface that combines a set of F ports connected to the same Fibre Channel node and operates as one link between the F ports and the NP ports. F port channels are mainly used to connect NX-OS Core and NPV switches to provide optimal bandwidth utilization and transparent failover between the uplinks of a VSAN. An F port channel trunk combines the functionality and advantages of a TF port and an F port channel.
Port channels also can form between the following set of ports:
E ports and TE ports
F ports and NP ports
TF ports and TNP ports
A port can be configured as a member of a static port channel only if the following configurations are the same in the port and the port channel: