Chapter 40
Configuring IP Unicast Routing
Figure 40-3
128.20.1.0
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
Step 1
configure terminal
Step 2
no ip classless
Step 3
end
Step 4
show running-config
Step 5
copy running-config startup-config
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.
In a switch stack, network communication uses a single MAC address and the IP address of the stack.
Note
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.
OL-9775-08
No IP Classless Routing
128.0.0.0/8
128.20.0.0
128.20.2.0
128.20.4.1
128.20.4.1
Bit bucket
128.20.3.0
Host
Purpose
Enter global configuration mode.
Disable classless routing behavior.
Return to privileged EXEC mode.
Verify your entry.
(Optional) Save your entry in the configuration file.
Catalyst 3750-E and 3560-E Switch Software Configuration Guide
Configuring IP Addressing
40-9