13-6
Catalyst 3750-X and 3560-X Switch Software Configuration Guide
OL-21521-01
Chapter 13 Configuring Interface Characteristics
Interface Types
Note The LAN base feature set does not support routing. The IP base feature set supports static routing and
RIP. For more advanced routing or for fallback bridging, enable the IP services feature set on the
standalone switch or the stack master. For information about using the software activation feature to
install a software license for a specific feature set, see the Cisco IOS Software Activation document.

SVI Autostate Exclude

The line state of an SVI with multiple ports on a VLAN is in the up state when it meets these conditions:
• The VLAN exists and is active in the VLAN database on the switch.
• 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.
Note 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.
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-an- 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. For information about configuring autostate exclude, see the “Configuring
SVI Autostate Exclude” section on page 13-39.
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, group multiple access ports into one logical access port,
group multiple tunnel ports into one logical tunnel port, or group multiple routed ports into one logical
routed 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 3 interfaces, you manually create the logical interface by using the
interface port-channel global configuration command. Then you manually assign an interface to the
EtherChannel by using the channel-group interface configuration command. 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. For more information, see
Chapter 40, “Configuring EtherChannels and Link-State Tracking.”