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Understanding Interface Types
is in the allowed list for a trunk port, the trunk port automatically becomes a member of that VLAN and
traffic is forwarded to and from the trunk port for that VLAN. If VTP learns of a new, enabled VLAN
that is not in the allowed list for a trunk port, the port does not become a member of the VLAN, and no
traffic for the VLAN is forwarded to or from the port.
For more information about trunk ports, see
Tunnel Ports
Tunnel ports are used in IEEE 802.1Q tunneling to segregate the traffic of customers in a
service-provider network from other customers who are using the same VLAN number. You configure
an asymmetric link from a tunnel port on a service-provider edge switch to an IEEE 802.1Q trunk port
on the customer switch. Packets entering the tunnel port on the edge switch, already
IEEE 802.1Q-tagged with the customer VLANs, are encapsulated with another layer of an IEEE 802.1Q
tag (called the metro tag), containing a VLAN ID unique in the service-provider network, for each
customer. The double-tagged packets go through the service-provider network keeping the original
customer VLANs separate from those of other customers. At the outbound interface, also a tunnel port,
the metro tag is removed, and the original VLAN numbers from the customer network are retrieved.
Tunnel ports cannot be trunk ports or access ports and must belong to a VLAN unique to each customer.
For more information about tunnel ports, see
Protocol Tunneling."
Routed Ports
A routed port is a physical port that acts like a port on a router; it does not have to be connected to a
router. A routed port is not associated with a particular VLAN, as is an access port. A routed port behaves
like a regular router interface, except that it does not support VLAN subinterfaces. Routed ports can be
configured with a Layer 3 routing protocol. A routed port is a Layer 3 interface only and does not support
Layer 2 protocols, such as DTP and STP.
Configure routed ports by putting the interface into Layer 3 mode with the no switchport interface
configuration command. Then assign an IP address to the port, enable routing, and assign routing
protocol characteristics by using the ip routing and router protocol global configuration commands.
Entering a no switchport interface configuration command shuts down the interface and then re-enables
Note
it, which might generate messages on the device to which the interface is connected. When you put an
interface that is in Layer 2 mode into Layer 3 mode, the previous configuration information related to
the affected interface might be lost.
The number of routed ports that you can configure is not limited by software. However, the
interrelationship between this number and the number of other features being configured might impact
CPU performance because of hardware limitations. See the
page 9-19
For more information about IP unicast routing and routing protocols, see
Unicast Routing."
Cisco Catalyst Blade Switch 3020 for HP Software Configuration Guide
9-4
for information about what happens when hardware resource limitations are reached.
Chapter 9
Chapter 11, "Configuring VLANs."
Chapter 15, "Configuring IEEE 802.1Q and Layer 2
"Configuring Layer 3 Interfaces" section on
Configuring Interface Characteristics
Chapter 34, "Configuring IP
OL-8915-03
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