IBM 12.1(22)EA6 User Manual
24-6
Cisco Systems Intelligent Gigabit Ethernet Switch Modules for the IBM BladeCenter, Software Configuration Guide
24R9746
Chapter 24 Configuring EtherChannels and Layer 2 Trunk Failover
Understanding EtherChannels
PAgP sends and receives PAgP PDUs only from interfaces that have PAgP enabled for the auto or
desirable mode. LACP sends and receives LACP PDUs only from interfaces that have LACP enabled
for the active or passive mode.
desirable mode. LACP sends and receives LACP PDUs only from interfaces that have LACP enabled
for the active or passive mode.
EtherChannel On Mode
EtherChannel on mode can be used to manually configure an EtherChannel. The on mode forces a port
to join an EtherChannel without negotiations. It can be useful if the remote device does not support
PAgP or LACP. With the on mode, a usable EtherChannel exists only when both ends of the link are
configured in the on mode.
to join an EtherChannel without negotiations. It can be useful if the remote device does not support
PAgP or LACP. With the on mode, a usable EtherChannel exists only when both ends of the link are
configured in the on mode.
Ports that are configured with on mode in the same channel group must have compatible port
characteristics, such as speed and duplex. Ports that are not compatible are suspended, even though they
are configured with on mode.
characteristics, such as speed and duplex. Ports that are not compatible are suspended, even though they
are configured with on mode.
Caution
You should exercise care when using the on mode. This is a manual configuration, and ports on both
ends of the EtherChannel must have a similar configuration. If the group is misconfigured, packet loss
or spanning-tree loops can occur.
ends of the EtherChannel must have a similar configuration. If the group is misconfigured, packet loss
or spanning-tree loops can occur.
Understanding Load Balancing and Forwarding Methods
EtherChannel balances the traffic load across the links in a channel by randomly associating a newly
learned MAC address with one of the links in the channel.
learned MAC address with one of the links in the channel.
EtherChannel balances the traffic load across the links in a channel by reducing part of the binary pattern
formed from the frame addresses to a numerical value that selects one of the links in the channel.
EtherChannel load balancing can use MAC addresses or IP addresses, source or destination addresses,
or both source and destination addresses. The selected mode applies to all EtherChannels configured on
the switch. You configure the load balancing and forwarding method by using the port-channel
load-balance global configuration command.
formed from the frame addresses to a numerical value that selects one of the links in the channel.
EtherChannel load balancing can use MAC addresses or IP addresses, source or destination addresses,
or both source and destination addresses. The selected mode applies to all EtherChannels configured on
the switch. You configure the load balancing and forwarding method by using the port-channel
load-balance global configuration command.
With source-MAC address forwarding, packets forwarded to an EtherChannel are distributed across the
ports in the channel based on the source-MAC address of the incoming packet. Therefore, to provide
load balancing, packets from different hosts use different ports in the channel, but packets from the same
host use the same port in the channel. The MAC address learned by the switch does not change.
ports in the channel based on the source-MAC address of the incoming packet. Therefore, to provide
load balancing, packets from different hosts use different ports in the channel, but packets from the same
host use the same port in the channel. The MAC address learned by the switch does not change.
With destination-MAC address forwarding, packets forwarded to an EtherChannel are distributed across
the ports in the channel based on the destination host MAC address of the incoming packet. Therefore,
packets to the same destination are forwarded over the same port, and packets to a different destination
might be sent on a different port in the channel. You configure the load balancing and forwarding method
by using the port-channel load-balance global configuration command.
the ports in the channel based on the destination host MAC address of the incoming packet. Therefore,
packets to the same destination are forwarded over the same port, and packets to a different destination
might be sent on a different port in the channel. You configure the load balancing and forwarding method
by using the port-channel load-balance global configuration command.
Different load-balancing methods have different advantages. You should choose a particular
load-balancing method based on the position of the switch in the network and the kind of traffic that
needs to be load-distributed. In
load-balancing method based on the position of the switch in the network and the kind of traffic that
needs to be load-distributed. In
, an EtherChannel of four workstations communicates with
a router. Because the router is a single-MAC-address device, source-based forwarding on the switch
EtherChannel ensures that the switch uses all available bandwidth to the router. The router is configured
for destination-based forwarding because the large number of workstations ensures that the traffic is
evenly distributed from the router EtherChannel.
EtherChannel ensures that the switch uses all available bandwidth to the router. The router is configured
for destination-based forwarding because the large number of workstations ensures that the traffic is
evenly distributed from the router EtherChannel.