28-7
Catalyst 3750 MetroSwitch Software Configuration Guide
78-15870-01
Chapter 28 Configuring IP Unicast Routing
Configuring IP Addressing
In Figure 28-3, the router in network 128.20.0.0 is connected to subnets 128.20.1.0, 128.20.2.0, and
128.20.3.0. If the host sends a packet to 120.20.4.1, because there is no network default route, the router
discards the packet.
Figure 28-3 No IP Classless Routing
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:
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.
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 determine the MAC address of the device. The process of
determining the MAC address from an IP address is called address resolution. The process of
determining the IP address from the MAC address is called reverse address resolution.
Host
128.20.1.0
128.20.2.0
128.20.3.0
128.20.4.1
128.0.0.0/8
128.20.4.1
Bit bucket
45748
128.20.0.0
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 Next Page
Loading...
Need help?
General
