Cisco Systems 3750E manual Configuring Address Resolution Methods, 38-9

Chapter 38 Configuring IP Unicast Routing

Configuring IP Addressing

Figure 38-3 No IP Classless Routing

128.0.0.0/8

128.20.0.0

128.20.1.0

128.20.2.0

128.20.4.1

Bit bucket

128.20.3.0

128.20.4.1

Host 45748

To prevent the switch from forwarding packets destined for unrecognized subnets to the best supernet route possible, you can disable classless routing behavior.

Beginning in privileged EXEC mode, follow these steps to disable classless routing:

	Command	Purpose
Step 1
	configure terminal	Enter global configuration mode.
Step 2
	no ip classless	Disable classless routing behavior.
Step 3
	end	Return to privileged EXEC mode.
Step 4
	show running-config	Verify your entry.
Step 5
	copy running-config startup-config	(Optional) Save your entry in the configuration file.

To restore the default and have the switch forward packets destined for a subnet of a network with no network default route to the best supernet route possible, use the ip classless global configuration command.

Configuring Address Resolution Methods

You can control interface-specific handling of IP by using address resolution. A device using IP can have both a local address or MAC address, which uniquely defines the device on its local segment or LAN, and a network address, which identifies the network to which the device belongs.

Note In a Catalyst 3750-E switch stack, network communication uses a single MAC address and the IP address of the stack.

The local address or MAC address is known as a data link address because it is contained in the data link layer (Layer 2) section of the packet header and is read by data link (Layer 2) devices. To communicate with a device on Ethernet, the software must learn the MAC address of the device. The process of learning the MAC address from an IP address is called address resolution. The process of learning the IP address from the MAC address is called reverse address resolution.

Catalyst 3750-E and 3560-E Switch Software Configuration Guide

OL-9775-02 38-9