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Cisco ME 3400 EthernetAccess Switch SoftwareConfiguration Guide
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Chapter9 Configuring Interface Cha rac teristics Understanding Interface Types
Note Entering a no switchport interface configuration command shuts down the interface and then re-enables
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 f eatur es b ein g c onfigure d mig ht i mp act
CPU performance because of hardware limitations. See the “Configuring Layer 3 Interfaces” section on
page 9-20 for information about what happens when hardware resource limitations are re ached.
For more information about IP unicast and multicast routing and r outi ng prot ocol s, se e Chapt er 32,
“Configuring IP Unicast Routing” and Chapter 34, “Configuring IP Multicast Routing.”
Note For full Layer 3 routing, you must have the metro IP access image installed on the switch
Switch Virtual Interfaces
A switch virtual interface (SVI) represents a VLAN of switch ports as one interface to the routing or
bridging function in the system. Only one SVI can be associated with a VLAN, but you need to configure
an SVI for a VLAN only when you wish to route between V LANs or to provide IP host connectivity to
the switch. By default, an SVI is created for the default VLAN (VLAN 1) to permit remote switch
administration. Additional SVIs must be explicitly configured.
Note You cannot delete interface VLAN 1.
SVIs provide IP host connectivity only to the system; in Layer 3 mode, you can configure routing across
SVIs.
Although the switch supports a total of 1005 VLANs (and SVIs), the interrelationship between th e
number of SVIs and routed ports and the number of other f eatures being configured might impact CPU
performance because of hardware limitations. See the “Configuring Layer 3 Interfaces” section on
page 9-20 for information about what happens when hardware resource limitations are re ached.
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 asso ci at ed wi th d ata f ra mes o n an IE EE 802.1Q
encapsulated trunk or the VLAN ID configured for an acc ess po rt. C onf ig ure a VLAN inter fa ce 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 3-9.
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 I P r outi ng, s ee Chapter 32,
“Configuring IP Unicast Routing,” and Chapter 34, “Configuring IP Multicast Routing.”
Note Routed ports (or SVIs) are supported only when the metro IP access image is installed on the switch.