Logical Layer 3 Vlan Interfaces - Cisco Catalyst 4500 Series Software Configuration Manual

About Layer 3 Interfaces
This section contains the following subsections:
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Logical Layer 3 VLAN Interfaces

The logical Layer 3 VLAN interfaces provide logical routing interfaces to VLANs on Layer 2 switches.
A traditional network requires a physical interface from a router to a switch to perform inter-VLAN
routing. The Catalyst 4500 series switch supports inter-VLAN routing by integrating the routing and
bridging functions on a single Catalyst 4500 series switch.
Figure 35-1
network are performed logically on one Catalyst 4500 series switch.
Figure 35-1
Interface Ethernet
VLAN1
Physical Layer 3 Interfaces
The physical Layer 3 interfaces support capabilities equivalent to a traditional router. These Layer 3
interfaces provide hosts with physical routing interfaces to a Catalyst 4500 series switch.
Figure 35-2
Catalyst 4500 Series Switch, Cisco IOS Software Configuration Guide - Cisco IOS XE 3.9.xE and IOS 15.2(5)Ex
35-2
Logical Layer 3 VLAN Interfaces, page 35-2
Physical Layer 3 Interfaces, page 35-2
Understanding SVI Autostate Exclude, page 35-3
Understanding Layer 3 Interface Counters, page 35-3
shows how the routing and bridging functions in the three physical devices of the traditional
Logical Layer 3 VLAN Interfaces for the Catalyst 4500 Series Switch
Router
Interface Ethernet
1.1.1.1 2.1.1.1
L2 Switch L2 Switch
VLAN2
Host 1 Host 2
Traditional network topology for routing
between VLANS
shows how the Catalyst 4500 series switch functions as a traditional router.
Chapter 35 Configuring Layer 3 Interfaces
Routing
Interface VLAN1 Interface VLAN2
1.1.1.1 2.1.1.1
VLAN1
Host 1
Logical Inter-VLAN routing on a single
Catalyst 4500 series switch
VLAN2
Host 2