Dynamic Link Aggregation; Usage Notes; Configuration Rules - HP 9304m Installation And Getting Started Manual

Installation and Getting Started Guide

Dynamic Link Aggregation

The software supports the IEEE 802.3ad standard for link aggregation. This standard describes the Link
Aggregation Control Protocol (LACP), a mechanism for allowing ports on both sides of a redundant link to
configure themselves into a trunk link (aggregate link), without the need for manual configuration of the ports into
trunk groups.
When you enable link aggregation on a group of HP ports, the HP ports can negotiate with the ports at the remote
ends of the links to establish trunk groups.

Usage Notes

• You cannot use 802.3ad link aggregation on a port configured as a member of a static trunk group.
• This feature is supported only for 10/100 and Gigabit Ethernet ports.
• When the feature dynamically adds or changes a trunk group, the show trunk command displays the trunk
as both configured and active. However, the show running-config or write terminal command does not
contain a trunk command defining the new or changed trunk group.
• If the feature places a port into a trunk group as a secondary port, all configuration information except
information related to link aggregation is removed from the port. For example, if port 1/3 has an IP interface,
and the link aggregation feature places port 1/3 into a trunk group consisting of ports 1/1 – 1/4, the IP
interface is removed from the port.
• If you use this feature on a Routing Switch that is running OSPF or BGP4, the feature causes these protocols
to reset when a dynamic link change occurs. The reset includes ending and restarting neighbor sessions with
OSPF and BGP4 peers, and clearing and relearning dynamic route entries and forwarding cache entries.
Although the reset causes a brief interruption, the protocols automatically resume normal operation.

Configuration Rules

HP ports follow the same configuration rules for dynamically created aggregate links as they do for statically
configured trunk groups. For example, each aggregate link must start on a primary port (the first port in a two- or
four-port range) and can contain either two or four ports, and so on. See "Trunk Group Rules" on page 5-3 and
"Trunk Group Load Sharing" on page 5-7.
Figure 5.6 on page 5-19 shows some examples of valid aggregate links.
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