Classless Routing - Cisco Catalyst 3750-E Software Configuration Manual
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Also See for Catalyst 3750-E:
- Getting started manual (27 pages) ,
- Product support bulletin (6 pages) ,
- Configuration handbook (359 pages)
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Configuring IP Addressing
Classless Routing
By default, classless routing behavior is enabled on the switch when it 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 consists of contiguous blocks of Class C
address spaces used to simulate 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 40-2
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.
Catalyst 3750-E and 3560-E Switch Software Configuration Guide
40-8
40-2, 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
40-3, 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 40
Configuring IP Unicast Routing
OL-9775-08
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Troubleshooting
