Technical data

Switching and Routing

• Interface parameters:

• Area membership

• Authentication (simple password or MD5)

• Link cost

• Interface priority

• Retransmit interval, transit delay, and dead interval

For information about the OSPF features and how to configure them, see the "Configuring OSPF" chapter in the

Foundry Enterprise Configuration and Management 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 Brocade ports, the Brocade ports can negotiate with the ports at

the remote ends of the links to establish trunk groups.

Configuration Rules

• Use the link aggregation feature only if the device at the other end of the links you want to aggregate also

supports IEEE 802.3ad link aggregation. Otherwise, you need to manually configure the trunk links.

• You cannot use 802.3ad link aggregation on a port configured as a member of a static trunk group.

• Link aggregation support is disabled by default. You can enable the feature on an individual port basis, in

active or passive mode.

• Brocade recommends that you disable or remove the cables from the ports you plan to enable for dynamic

link aggregation. Doing so prevents the possibility that LACP will use a partial configuration to talk to the

other side of a link. A partial configuration does not cause errors, but does sometimes require LACP to be

disabled and re-enabled on both sides of the link to ensure that a full configuration is used. It's easier to

disable a port or remove its cable first. This applies both for active link aggregation and passive link

aggregation.

• Active mode – When you enable a port for active link aggregation, the Brocade port can exchange standard

LACP Protocol Data Unit (LACPDU) messages to negotiate trunk group configuration with the port on the

other side of the link. In addition, the Brocade port actively sends LACPDU messages on the link to search

for a link aggregation partner at the other end of the link, and can initiate an LACPDU exchange to negotiate

link aggregation parameters with an appropriately configured remote port.

• Passive mode – When you enable a port for passive link aggregation, the Brocade port can exchange

LACPDU messages with the port at the remote end of the link, but the Brocade port cannot search for a link

aggregation port or initiate negotiation of an aggregate link. Thus, the port at the remote end of the link must

initiate the LACPDU exchange.

• 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 link aggregation 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 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 system running Router code 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