Reference Guide

424 | Interfaces
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Port channels can contain a mix of 10, 100, or 1000 Mbps Ethernet interfaces and Gigabit Ethernet
interfaces, and the interface speed (10, 100, or 1000 Mbps) used by the port channel is determined by the
first port channel member that is physically up. FTOS disables the interfaces that do match the interface
speed set by the first channel member. That first interface may be the first interface that is physically
brought up or was physically operating when interfaces were added to the port channel. For example, if the
first operational interface in the port channel is a Gigabit Ethernet interface, all interfaces at 1000 Mbps are
kept up, and all 10/100/1000 interfaces that are not set to 1000 speed or auto negotiate are disabled.
FTOS brings up 10/100/1000 interfaces that are set to auto negotiate so that their speed is identical to the
speed of the first channel member in the port channel.
10/100/1000 Mbps interfaces in port channels
When both 10/100/1000 interfaces and GigE interfaces are added to a port channel, the interfaces must
share a common speed. When interfaces have a configured speed different from the port channel speed, the
software disables those interfaces.
The common speed is determined when the port channel is first enabled. At that time, the software checks
the first interface listed in the port channel configuration. If that interface is enabled, its speed
configuration becomes the common speed of the port channel. If the other interfaces configured in that port
channel are configured with a different speed, FTOS disables them.
For example, if four interfaces (Gi 0/0, 0/1, 0/2, 0/3) in which Gi 0/0 and Gi 0/3 are set to speed 100 Mb/s
and the others are set to 1000 Mb/s, with all interfaces enabled, and you add them to a port channel by
entering
channel-member gigabitethernet 0/0-3 while in the port channel interface mode, and FTOS
determines if the first interface specified (Gi 0/0) is up. Once it is up, the common speed of the port
channel is 100 Mb/s. FTOS disables those interfaces configured with speed 1000 or whose speed is 1000
Mb/s as a result of auto-negotiation.
In this example, you can change the common speed of the port channel by changing its configuration so the
first enabled interface referenced in the configuration is a 1000 Mb/s speed interface. You can also change
the common speed of the port channel here by setting the speed of the Gi 0/0 interface to 1000 Mb/s.
Configuration task list for port channel interfaces
To configure a port channel (LAG), you use the commands similar to those found in physical interfaces.
By default, no port channels are configured in the startup configuration.
• Create a port channel (mandatory)
• Add a physical interface to a port channel (mandatory)
• Reassign an interface to a new port channel (optional)
• Configure the minimum oper up links in a port channel (LAG) (optional)
• Add or remove a port channel from a VLAN (optional)
• Assign an IP address to a port channel (optional)
• Delete or disable a port channel (optional)
• Load balancing through port channels (optional)