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Static lacp trunks, Dynamic lacp trunks, Vlans and dynamic lacp – HP 2600 User Manual

Page 250: Stp and igmp

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Port Trunking
Port Status and Configuration

Static LACP Trunks.

Where a port is configured for LACP (Active or

Passive), but does not belong to an existing trunk group, you can add that port
to a static trunk. Doing so disables dynamic LACP on that port, which means
you must manually configure both ends of the trunk.

Dynamic LACP Trunks.

You can configure a port for LACP-active or LACP-

passive, but on a dynamic LACP trunk you cannot configure the other options
that you can on static trunks. If you want to manually configure a trunk, use
the

trunk command. (Refer to “Using the CLI To Configure a Static or Dynamic

Trunk Group” on page 12-15.)

VLANs and Dynamic LACP.

A dynamic LACP trunk operates only in the

default VLAN (unless you have enabled GVRP on the switch and use

Forbid to

prevent the ports from joining the default VLAN).

If you want to use LACP for a trunk on a non-default VLAN and GVRP is
disabled, configure the trunk as a static trunk.

If there are ports that you do not want on the default VLAN, ensure that
they cannot become dynamic LACP trunk members. Otherwise a traffic
loop can unexpectedly occur. For example:

VLAN-1

(Default

VLAN)

VLAN-2

VLAN-1

(Default

VLAN)

VLAN-2

VLAN-1

(Default

VLAN)

VLAN-2

VLAN-1

(Default

VLAN)

VLAN-2

If the ports in VLAN 2 are configured to allow a dynamic trunk (and GVRP is disabled), adding a
second link in VLAN 2 automatically forms a dynamic LACP trunk and moves the trunk to VLAN-1
(the default VLAN), which creates a traffic loop in VLAN 1 between the two switches and
eliminates the link in VLAN 2 between the two switches.

Figure 12-11. A Dynamic LACP Trunk Forming in a VLAN Can Cause a Traffic Loop

Easy control methods include either disabling LACP on the selected ports or
configuring them to operate in static LACP trunks.

STP and IGMP.

If spanning tree (STP) and/or IGMP is enabled in the switch,

a dynamic LACP trunk operates only with the default settings for these
features and does not appear in the port listings for these features.

12-24

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