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Cisco ME 3400 Ethernet Access Switch Software Configuration Guide
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Chapter 9 Configuring Interfaces
Understanding Interface Types
Although the switch supports a total of 1005 VLANs (and SVIs), the interrelationship between the
number of SVIs and routed ports and the number of other features being configured might impact CPU
performance because of hardware limitations. See the “Configuring Layer 3 Interfaces” section on
page 9-22 for information about what happens when hardware resource limitations are reached.
SVIs are created the first time that you enter the vlan interface configuration command for a VLAN
interface. The VLAN corresponds to the VLAN tag associated with data frames on an IEEE 802.1Q
encapsulated trunk or the VLAN ID configured for an access port. Configure a VLAN interface for each
VLAN for which you want to route traffic, and assign it an IP address. For more information, see the
“Manually Assigning IP Information” section on page 3-14.
Note When you create an SVI, it does not become active until it is associated with a physical port.
SVIs support routing protocols. For more information about configuring IP routing, see Chapter 35,
“Configuring IP Unicast Routing,” and Chapter 40, “Configuring IP Multicast Routing.”
Note Routed ports (or SVIs) are supported only when the metro IP access image is installed on the switch.
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 Cisco Discovery Protocol (CDP),
Link Aggregation Control Protocol (LACP), and the Port Aggregation Protocol (PAgP), which operate
only on physical NNI or ENI 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 34, “Configuring EtherChannels and Link-State Tracking.”
Dual-Purpose Ports
Twelve ports on the ME 3400-12CS and two ports on the ME 3400-2CS switches are dual-purpose ports
that can be configured as 10/100/100 ports or as small form-factor pluggable (SFP) module ports. Each
dual-purpose port is considered as a single interface with dual front ends (an RJ-45 connector and an
SFP module connector). The dual front ends are not redundant interfaces; the switch activates only one
connector of the pair.