Cisco WS-C2960S-24PD-L Software Guide - Page 206

Creating EtherChannel Port Groups Chapter 7 Configuring the Switch Ports Understanding EtherChannel Port Grouping This software release supports two different types of port groups: source-based forwarding port groups and destination-based forwarding port groups. Source-based forwarding port groups distribute packets forwarded to the group based on the source address of incoming packets. You can configure up to eight ports in a source-based forwarding port group. Source-based forwarding is enabled by default. Destination-based port groups distribute packets forwarded to the group based on the destination address of incoming packets. You can configure an unlimited number of ports in a destination-based port group. You can create up to 12 port groups. All ports in each group must be of the same type; for example, they must be all source-based or all destination-based. You can have source-based port groups and destination-based source groups. You can independently configure port groups that link switches, but you must consistently configure both ends of a port group. In Figure 7-1, a port group of two workstations communicates with a router. Because the router is a single-MAC-address device, source-based forwarding ensures that the switch uses all available bandwidth to the router. The router is configured for destination-based forwarding because the large number of stations ensures that the traffic is evenly distributed through the port-group ports on the router. Figure 7-1 Source-Based Forwarding Source-based forwarding Destination-based forwarding FEC port group Catalyst 2900 XL or Catalyst 3500 XL switch Cisco router 12650 The switch treats the port group as a single logical port; therefore, when you create a port group, the switch uses the configuration of the first port for all ports added to the group. If you add a port and change the forwarding method, it changes the forwarding for all ports in the group. After the group is created, changing STP or VLAN membership parameters for one port in the group automatically changes the parameters for all ports. Each port group has one port that carries all unknown multicast, broadcast, and STP packets. Port Group Restrictions on Static-Address Forwarding These restrictions apply to entering static addresses that are forwarded to port groups: • If the port group forwards based on the source MAC address (the default), configure the static address to forward to all ports in the group. This method eliminates the chance of lost packets. • If the port group forwards based on the destination address, configure the static address to forward to only one port in the port group. This method avoids the possible transmission of duplicate packets. For more information, see the "Adding Static Addresses" section on page 6-19. Catalyst 2900 Series XL and Catalyst 3500 Series XL Software Configuration Guide 7-8 78-6511-08