Classless Routing - Cisco WS-CBS3032-DEL Software Configuration Manual

Configuring IP Addressing

Classless Routing

By default, classless routing is enabled when the switch is configured to route. With classless routing, if
a router receives packets for a subnet of a network with no default route, the router forwards the packet
to the best supernet route. A supernet is contiguous blocks of Class C address spaces simulating a single,
larger address space and is designed to relieve the pressure on the rapidly depleting Class B address
space.
In Figure
discarding the packet, the router forwards it to the best supernet route. If you disable classless routing
and a router receives packets destined for a subnet of a network with no network default route, the router
discards the packet.
Figure 39-2
128.20.1.0
In Figure
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.
Cisco Catalyst Blade Switch 3130 and 3032 for Dell Software Configuration Guide
39-8
39-2, classless routing is enabled. When the host sends a packet to 120.20.4.1, instead of
IP Classless Routing
128.0.0.0/8
128.20.4.1
128.20.0.0 IP classless
128.20.2.0
128.20.4.1
39-3, 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
Host
Chapter 39 Configuring IP Unicast Routing
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