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Cisco ME 3800X and 3600X Switch Software Configuration Guide
OL-23400-01
Chapter 9 Configuring Interfaces
Understanding Interface Types
NNI Port Type
All Cisco ME 3800X and 3600X ports are network node interfaces (NNIs), which are typically
connected to a router or to another switch. The default status for an NNI is administratively up to allow
a service provider remote access to the switch during initial configuration.
Port-Based VLANs
A VLAN is a switched network that is logically segmented by function, team, or application, without
regard to the physical location of the users. For more information about VLANs, see
Chapter 10,
“Configuring VLANs.”
Packets received on a port are forwarded only to ports that belong to the same
VLAN as the receiving port. Network devices in different VLANs cannot communicate with one another
without a Layer 3 device to route traffic between the VLANs.
VLAN partitions provide hard firewalls for traffic in the VLAN, and each VLAN has its own MAC
address table. A VLAN comes into existence when a local port is associated with the VLAN ID or when
a user creates te VLAN ID.
To configure VLANs, use the vlan vlan-id global configuration command to enter VLAN configuration
mode. The VLAN configurations for VLAN IDs 1 to 1005 are saved in the VLAN database.
Extended-range VLANs (VLAN IDs 1006 to 4094) are not added to the VLAN database. VLAN
configuration is saved in the switch running configuration, and you can save it in the switch startup
configuration file by entering the copy running-config startup-config privileged EXEC command.
Add ports to a VLAN by using the switchport interface configuration commands:
•
Identify the interface.
•
For a trunk port, set trunk characteristics, and if desired, define the VLANs to which it can belong.
•
For an access port, set and define the VLAN to which it belongs.
To isolate VLANs of different customers in a service-provider network, Cisco ME switches use UNI
VLANs. Local switching does not occur among user network interfaces (UNIs) and enhanced network
interfaces (ENIs) on the switch that belong to the same UNI isolated VLAN. Local switching is allowed
among ports that belong to a UNI community VLAN. Because all ports on the ME 3800X and 3600X
switches are NNIs, UNI VLAN configuration has no effect. Local switching is allowed between NNIs.
Switch Ports
Switch ports are Layer 2 only interfaces associated with a physical port. Switch ports belong to one or
more VLANs. You can configure a port as an access port or trunk port. Switch ports are used for
managing the physical interface and associated Layer 2 protocols and do not handle routing or bridging.
Configure switch ports by using the switchport interface configuration commands. Use the switchport
command with no keywords to put an interface that is in Layer 3 mode into Layer 2 mode.
Note
When you put an interface that is in Layer 3 mode into Layer 2 mode, the previous configuration
information related to the affected interface might be lost, and the interface is returned to its default
configuration.
For detailed information about configuring access port and trunk port characteristics, see
Chapter 10,
“Configuring VLANs.”
