Cisco Nexus 5000 Series Switch Fabric Manager Software Configuration Guide, NX-OS 4.0 (OL-16598-01, June 2008)

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14-17
Nexus 5000 Series Switch Fabric Manager Software Configuration Guide
OL-16598-01
Chapter 14 Configuring SAN Port Channels
Port Channel Protocol
Autocreation Guidelines
When using the autocreation protocol, follow these guidelines:
• A port is not allowed to be configured as part of a SAN port channel when the autocreation feature
is enabled. These two configurations are mutually exclusive.
• Autocreation must be enabled in both the local and peer ports to negotiate a SAN port channel.
• Aggregation occurs in one of two ways:
– A port is aggregated into a compatible autocreated SAN port channel.
– A port is aggregated with another compatible port to form a new SAN port channel.
• Newly created SAN port channels are allocated from the maximum possible port channel number in
a decreasing order based on availability. If all port channel numbers are used up, aggregation is not
allowed.
• You cannot change the membership or delete an autocreated SAN port channel.
• When you disable autocreation, all member ports are removed from the autocreated SAN port
channel.
• Once the last member is removed from an autocreated SAN port channel, the channel is
automatically deleted and the number is released for reuse.
• An autocreated SAN port channel is not persistent through a reboot. An autocreated SAN port
channel can be manually configured to appear the same as a persistent SAN port channel. Once the
SAN port channel is made persistent, the autocreation feature is disabled in all member ports.
• You can enable or disable the autocreation feature on a per-port basis or for all ports in the switch.
When this configuration is enabled, the channel group mode is assumed to be active. The default for
this task is disabled.
• If autocreation of channel groups is enabled for an interface, you must first disable autocreation
before downgrading to earlier software versions or before configuring the interface in a manually
configured channel group.
Tip When enabling autocreation in any switch in the Nexus 5000 Series, we recommend that you retain at
least one interconnected port between the switches without any autocreation configuration. If all ports
between two switches are configured with the autocreation feature at the same time, a possible traffic
disruption may occur between these two switches as ports are automatically disabled and reenabled
when they are added to an autocreated SAN port channel.
Enabling and Configuring Autocreation
To configure port channel autocreation, check the Dynamically form Port Channel Group from
selected ISLs option in the Port Channel Wizard. See the “Configuring SAN Port Channels” section on
page 14-7.