232 | Interfacesw w w . d e l l . c o m | s u p p o r t . d e l l . c o m Table 13-2 lists the number of port channels per platform.As soon as a port channel is configured, FTOS treats it like a physical interface. For example, IEEE802.1Q tagging is maintained while the physical interface is in the port channel.Member ports of a LAG are added and programmed into hardware in a predictable order based on the portID, instead of in the order in which the ports come up. With this implementation, load balancing yieldspredictable results across switch 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 100, 1000, or 10000 Mbps Ethernet interfaces and TenGigabit Ethernetinterfaces. The interface speed (100, 1000, or 10000 Mbps) used by the port channel is determined by thefirst port channel member that is physically up. FTOS disables the interfaces that do not match theinterface speed set by the first channel member. That first interface may be the first interface that isphysically brought up or was physically operating when interfaces were added to the port channel. Forexample, if the first operational interface in the port channel is a TenGigabit Ethernet interface, allinterfaces at 1000 Mbps are kept up, and all 100/1000/10000 interfaces that are not set to 1000 Mbps speedor auto negotiate are disabled.100/1000/10000 Mbps Interfaces in Port ChannelsWhen both 100/1000/10000 interfaces and TenGigabitEthernet interfaces are added to a port channel, theinterfaces must share a common speed. When interfaces have a configured speed different from the portchannel speed, the software disables those interfaces.The common speed is determined when the port channel is first enabled. At that time, the software checksthe first interface listed in the port channel configuration. If that interface is enabled, its speedconfiguration becomes the common speed of the port channel. If the other interfaces configured in that portchannel are configured with a different speed, FTOS disables them.For example, if four interfaces (TenGig 0/0, 0/1, 0/2, 0/3) in which TenGig 0/0 and TenGig 0/3 are set tospeed 100 Mb/s and the others are set to 1000 Mb/s, with all interfaces enabled, and you add them to a portchannel by entering channel-member tengigabitethernet 0/0-3 while in port channel interface mode, and FTOSdetermines if the first interface specified (TenGig 0/0) is up. After it is up, the common speed of the portchannel is 100 Mb/s. FTOS disables those interfaces configured with speed 1000 Mb/s or whose speed is1000 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 thefirst enabled interface referenced in the configuration is a 1000 Mb/s speed interface. You can also changethe common speed of the port channel by setting the speed of the TenGig 0/0 interface to 1000 Mb/s.Table 13-2. Number of Port Channels per PlatformPlatform Port-channels Members/ChannelMXL 10/40GbE Switch IO Module 128 16
