At times the router might receive packets destined for a subnet of a network that has no network default route. To have the Cisco IOS software forward such packets to the best supernet route possible, use the ip classless global configuration command. To disable this feature, use the no form of this command.
ip classless
no ip classless
Syntax Description
This command has no arguments or keywords.
Default
Enabled
Command Mode
Global configuration
Usage Guidelines
This command first appeared in Cisco IOS Release 10.0. At Release 11.3, the default behavior changed from disabled to enabled.
This command allows the software to forward packets that are destined for unrecognized subnets of directly connected networks. The packets are forwarded to the best supernet route.
When this feature is disabled, the software discards the packets when a router receives packets for a subnet that numerically falls within its subnetwork addressing scheme, if there is no such subnet number in the routing table and there is no network default route.
Example
The following example prevents the software from forwarding packets destined for an unrecognized subnet to the best supernet possible:
no ip classless