Cisco Catalyst 2960 Series, Configuration Manual

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• The VLAN interface exists and is not administratively down.
•
At least one Layer 2 (access or trunk) port exists, has a link in the
up
state on this VLAN, and is in the
spanning-tree forwarding state on the VLAN.
The protocol link state for VLAN interfaces come up when the first switchport belonging to the
corresponding VLAN link comes up and is in STP forwarding state.
Note
The default action, when a VLAN has multiple ports, is that the SVI goes down when all ports in the VLAN
go down. You can use the SVI autostate exclude feature to configure a port so that it is not included in the
SVI line-state up-or-down calculation. For example, if the only active port on the VLAN is a monitoring port,
you might configure autostate exclude on that port so that the VLAN goes down when all other ports go down.
When enabled on a port,
autostate exclude
applies to all VLANs that are enabled on that port.
The VLAN interface is brought up when one Layer 2 port in the VLAN has had time to converge (transition
from STP listening-learning state to forwarding state). This prevents features such as routing protocols from
using the VLAN interface as if it were fully operational and minimizes other problems, such as routing black
holes.
EtherChannel Port Groups
EtherChannel port groups treat multiple switch ports as one switch port. These port groups act as a single
logical port for high-bandwidth connections between switches or between switches and servers. An
EtherChannel balances the traffic load across the links in the channel. If a link within the EtherChannel fails,
traffic previously carried over the failed link changes to the remaining links. You can group multiple trunk
ports into one logical trunk port or multiple access ports into one logical access port. Most protocols operate
over either single ports or aggregated switch ports and do not recognize the physical ports within the port
group. Exceptions are the DTP, the Cisco Discovery Protocol (CDP), and the Port Aggregation Protocol
(PAgP), which operate only on physical ports.
When you configure an EtherChannel, you create a port-channel logical interface and assign an interface to
the EtherChannel. For Layer 2 interfaces, use the
channel-group interface configuration command to
dynamically create the port-channel logical interface. This command binds the physical and logical ports
together.
Power over Ethernet Ports
A PoE-capable switch port automatically supplies power to one of these connected devices if the switch senses
that there is no power on the circuit:
• a Cisco pre-standard powered device (such as a Cisco IP Phone or a Cisco Aironet Access Point)
• an IEEE 802.3af-compliant powered device
A powered device can receive redundant power when it is connected to a PoE switch port and to an AC power
source. The device does not receive redundant power when it is only connected to the PoE port.
Using the Switch USB Ports
Theswitch has three USB ports on the front panel
—
a USB mini-Type B console port and two USB Type A
ports.
Consolidated Platform Configuration Guide, Cisco IOS Release 15.2(4)E (Catalyst 2960-X Switches)
18
Information About Configuring Interface Characteristics