Cisco Nexus 2000 Series Manual page 5

Overview
All members of the port channel must be Fabric Extender host interfaces and all host interfaces must be from
the same Fabric Extender. You cannot mix interfaces from the Fabric Extender and the parent switch.
Layer 2 mode is supported on host interface port channels.
You can configure Layer 2 port channels as access or trunk ports.
Beginning with Cisco NX-OS Release 5.2(1), Fabric Extenders support the host vPC feature where a server
can be dual-attached to two different FEXs through a port channel. You must configure parent switches that
connect each Fabric Extender (one parent switch per FEX) in a vPC domain.
Minimum Number of Links on a Fabric Port Channel
In a network configuration of dual-homed hosts (active/standby), you can configure the Fabric Extender to
support a minimum number of links for fabric port channels (FPCs) with the port-channel min-links command.
When the number of FPC links falls below the specified threshold, the host-facing Cisco Nexus 2000 interfaces
are brought down. This process allows for a NIC switchover on the connection between the host and the FEX.
The automatic recovery of Cisco Nexus 2000 Series interfaces to the standby FEX is triggered when the
number of FPC links reaches the specified threshold.
Load Balancing Using Host Interface Port Channels
The Cisco NX-OS software allows for load balancing traffic across all operational interfaces on a FEX host
interface port-channel by hashing the addresses in the frame to a numerical value that selects one of the links
in the channel. Port-channels provide load balancing by default.
You can configure the type of load-balancing algorithm used. You can choose the load-balancing algorithm
that determines which member port to select for egress traffic by looking at the fields in the frame.
You can configure the load-balancing mode to apply to all Fabric Extenders or to specified ones. If
load-balancing mode is not configured, Fabric Extenders use the default system configuration. The per-FEX
configuration takes precedence over the load-balancing configuration for the entire system. You cannot
configure the load-balancing method per port channel.
The default load-balancing mode for Layer 3 interfaces is the source and destination IP address, and the
Note
default load-balancing mode for non-IP interfaces is the source and destination MAC address. For more
details, see the Cisco Nexus 7000 Series NX-OS Interfaces Configuration Guide, Release 6.x.
You can configure the device to use one of the following methods to load balance across the port channel:
• Destination MAC address
• Source MAC address
• Source and destination MAC address
• Destination IP address
• Source IP address
• Source and destination IP address
• Source TCP/UDP port number
Cisco Nexus 2000 Series NX-OS Fabric Extender Software Configuration Guide for Cisco Nexus 7000 Series
Minimum Number of Links on a Fabric Port Channel
Switches, Release 5.2
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