Cisco Catalyst 4500 Series - About Layer 3 Interfaces

CHAPTER
32-1
Software Configuration Guide—Release IOS XE 3.3.0SG and IOS 15.1(1)SG
OL-25340-01
32
Configuring Layer 3 Interfaces
This chapter describes the Layer 3 interfaces on a Catalyst 4500 series switch. It also provides
guidelines, procedures, and configuration examples.
This chapter includes the following major sections:
• About Layer 3 Interfaces, page 32-1
• Configuration Guidelines, page 32-5
• Configuring Logical Layer 3 VLAN Interfaces, page 32-6
• Configuring VLANs as Layer 3 Interfaces, page 32-7
• Configuring Physical Layer 3 Interfaces, page 32-12
• Configuring EIGRP Stub Routing, page 32-13
Note For complete syntax and usage information for the switch commands used in this chapter, first look at
the Cisco Catalyst 4500 Series Switch Command Reference and related publications at this location:
http://www.cisco.com/en/US/products//hw/switches/ps4324/index.html
If the command is not found in the Catalyst 4500 Series Switch Command Reference, it will be found in
the larger Cisco IOS library. Refer to the Cisco IOS Command Reference and related publications at this
location:
http://www.cisco.com/en/US/products/ps6350/index.html
About Layer 3 Interfaces
The Catalyst 4500 family switch supports Layer 3 interfaces with the Cisco IOS IP and IP routing
protocols. Layer 3, the network layer, is primarily responsible for the routing of data in packets across
logical internetwork paths.
Layer 2, the data link layer, contains the protocols that control the physical layer (Layer 1) and how data
is framed before being transmitted on the medium. The Layer 2 function of filtering and forwarding data
in frames between two segments on a LAN is known as bridging.
The Catalyst 4500 series switch supports two types of Layer 3 interfaces. The logical Layer 3 VLAN
interfaces integrate the functions of routing and bridging. The physical Layer 3 interfaces allow the
Catalyst 4500 series switch to be configured like a traditional router.