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Catalyst 3560 Switch Software Configuration Guide
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Chapter 11 Configuring Interface Characteristics
Understanding Interface Types
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 or 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 11-25 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 ISL or
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 and bridging configurations. For more information about configuring IP
routing, see Chapter 36, “Configuring IP Unicast Routing,” Chapter 44, “Configuring IP Multicast
Routing,”and Chapter 46, “Configuring Fallback Bridging.”
Note The IP base image supports static routing and RIP; for more advanced routing or for fallback bridging,
you must have the IP services image installed on the switch.
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