Specifications

Load Sharing on the Switch
ExtremeWare XOS 11.0 Concepts Guide 75
VMAN ports can belong to load-sharing groups. If any port in the load-sharing group is enabled for
VMAN, all ports in the group are automatically enabled to handle jumbo size frames. Also, VMAN is
automatically enabled on all ports of the untagged load-sharing group.
Load-Sharing Algorithms
Load-sharing algorithms allow you to select the distribution technique used by the load-sharing group
to determine the output port selection. Algorithm selection is not intended for use in predictive traffic
engineering.
NOTE
Always reference the master logical port of the load-sharing group when configuring or viewing VLANs.
VLANs configured to use other ports in the load-sharing group will have those ports deleted from the
VLAN when load sharing is enabled.
You can configure one of two load-sharing algorithms on the switch, as follows:
• Port-based—Uses the ingress port to determine which physical port in the load-sharing group is
used to forward traffic out of the switch.
• Address-based—Uses addressing information to determine which physical port in the load-sharing
group to use to forward traffic out of the switch. Addressing information is based on the packet
protocol, as follows:
— IP packets—Uses the source and destination MAC and IP addresses and the TCP port number.
— All other packets—Uses the source and destination MAC address.
If you do not explicitly select an algorithm, the port-based scheme is used. However, the address-based
algorithm has a more even distribution and is the recommended choice (except when running
Multiprotocol Label Switching, in which case the port-based algorithm is recommended).
Address-Based Load Sharing
When you configure address-based load sharing, the switch examines a specific place in the packet to
determine which egress port to use for forwarding traffic:
• For Layer 2 load sharing, the switch uses the MAC source address and destination address.
• For Layer 3 load sharing, the switch uses the IP source address and destination address.
• For Layer 4 load sharing, the switch using the TCP source and destination port number.
You can control the field examined by the switch for address-based load sharing by using the following
command:
configure sharing address-based [L2 | L2_L3 | L2_L3_L4 |L2_L3_CHK_SUM |
L2_L3_L4_CHK_SUM]
where CHK SUM indicates that the switch should examine the IP check sum. Examining the IP check
sum in addition to the other parameters produces a random traffic pattern on the egress of the
load-shared links because the IP check sum includes the packet length, which is likely to change from
packet to packet.
This feature is available for the address-based load-sharing algorithm only. The selected address-based
algorithm is applied to the entire switch, to all the load-sharing groups configured as address-based.