Reference Guide

Port Channel Implementation
FTOS supports static and dynamic port channels.
• Static — Port channels that are statically configured.
• Dynamic — Port channels that are dynamically configured using the link aggregation control protocol (LACP).
For details, refer to Link Aggregation Control Protocol (LACP).
There are 128 port-channels with eight members per channel.
As soon as you configure a port channel, FTOS treats it like a physical interface. For example, IEEE 802.1Q tagging is
maintained while the physical interface is in the port channel.
Member ports of a LAG are added and programmed into the hardware in a predictable order based on the port ID,
instead of in the order in which the ports come up. With this implementation, load balancing yields predictable results
across line card resets and chassis reloads.
A physical interface can belong to only one port channel at a time.
Each port channel must contain interfaces of the same interface type/speed.
Port channels can contain a mix of 10, 100, or 1000 Mbps Ethernet interfaces and Gigabit Ethernet interfaces. The
interface speed (10, 100, or 1000 Mbps) the port channel uses is determined by the first port channel member that is
physically up. FTOS disables the interfaces that do match the interface speed that the first channel member sets. 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 you enabled that interface, 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 (TenGig 0/1, 0/2, 0/3 and 0/4) in which TenGig 0/1 and TenGig 0/2 are set to speed 1000
Mb/s and the others(te 0/3 and 0/4) are set to 10000 Mb/s, with all interfaces enabled, and you add them to a port
channel by entering channel-member tengigabitethernet 0/1-4 while in port channel interface mode,
and FTOS determines if the first interface specified (TenGig 0/1) is up. After it is up, the common speed of the port
channel is 1000 Mb/s. FTOS disables those interfaces configured with speed 10000 Mb/s or whose speed is 10000 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.
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