
Port Trunking
Trunk Group Operation Using LACP
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 13-14.)
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 13-11. 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.
Spanning Tree and IGMP. If Spanning Tree 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.
Half-Duplex and/or Different Port Speeds Not Allowed in LACP
Trunks. The ports on both sides of an LACP trunk must be configured for
the same speed and for full-duplex (FDx). The 802.3ad LACP standard speci-
fies a full-duplex (FDx) requirement for LACP trunking. (10-gigabit ports
operate only at FDx.)
13-23
Kommentare zu diesen Handbüchern