- Hewlett-Packard Switch User Manual

Port Trunking
Trunk Configuration Methods
Spanning Tree: 802.1D (STP) and 802.1w (RSTP) Spanning Tree operate as a global setting on the switch (with one instance
of Spanning Tree per switch). 802.1s (MSTP) Spanning Tree operates on a per-instance basis (with multiple instances
allowed per switch). For each SpanningTree instance, you can adjust Spanning Tree parameters on a per-port basis. A
static trunk of any type appears in the Spanning Tree configuration display, and you can configure Spanning Tree
parameters for a static trunk in the same way that you would configure Spanning Tree parameters on a non-trunked port.
(Note that the switch lists the trunk by name—such as Trk1—and does not list the individual ports in the trunk.) For
example, if ports C1 and C2 are configured as a static trunk named Trk1, they are listed in the Spanning Tree display as
Trk1 and do not appear as individual ports in the Spanning Tree displays.
In this example showing
part of the show spanning-
tree listing, ports C1 and C2
are members of TRK1 and
do not appear as individual
ports in the port
configuration part of the
listing.
Figure 12-3. Example of a Port Trunk in a Spanning Tree Listing
When Spanning Tree forwards on a trunk, all ports in the trunk will be forwarding. Conversely, when Spanning Tree blocks
a trunk, all ports in the trunk are blocked.
Note: A dynamic LACP trunk operates only with the default Spanning Tree settings. Also, this type of trunk appears in
the CLI show spanning-tree display, but not in the Spanning Tree Operation display
of the Menu interface.
If you remove a port from a static trunk, the port retains the same Spanning Tree settings that were configured for the trunk.
IP Multicast Protocol (IGMP): A static trunk of any type appears in the IGMP configuration display, and you can configure
IGMP for a static trunk in the same way that you would configure IGMP on a non-trunked port. (Note that the switch lists
the trunk by name—such as Trk1—and does not list the individual ports in the trunk.) Also, creating a new trunk
automatically places the trunk in IGMP Auto status if IGMP is enabled for the default VLAN. A dynamic LACP trunk
operates only with the default IGMP settings and does not appear in the IGMP configuration display or
show ip igmp
listing.
VLANs: Creating a new trunk automatically places the trunk in the DEFAULT_VLAN, regardless of whether the ports in
the trunk were in another VLAN. Similarly, removing a port from a trunk group automatically places the port in the default
VLAN. You can configure a static trunk in the same way that you configure a port for membership in any VLAN.
Note: For a dynamic LACP trunk to operate in a VLAN other than the default VLAN (DEFAULT_VLAN), GVRP must be
enabled. Refer to “Trunk Group Operation Using LACP” on page 12-18.
Port Security: Trunk groups (and their individual ports) cannot be configured for port security, and the switch excludes
trunked ports from the
show port-security listing. If you configure non-default port security settings for a port, then
subsequently try to place the port in a trunk, you will see the following message and the command will not be executed:
< port-list > Command cannot operate over a logical port.
Monitor Port:
Note: A trunk cannot be a monitor port. A monitor port can monitor a static trunk but cannot monitor a dynamic LACP trunk.
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