Cisco Systems 3560 Manual De Usuario

After configuring an IP interface address, you can enable routing and configure one or more routing 
protocols, or you can configure the way the switch responds to network broadcasts. A broadcast is a data 
packet destined for all hosts on a physical network. The switch supports two kinds of broadcasting: 

A directed broadcast packet is sent to a specific network or series of networks. A directed broadcast 
address includes the network or subnet fields.

A flooded broadcast packet is sent to every network.

You can also limit broadcast, unicast, and multicast traffic on Layer 2 interfaces by using the 
storm-control interface configuration command to set traffic suppression levels. For more information, 
see 

Routers provide some protection from broadcast storms by limiting their extent to the local cable. 
Bridges (including intelligent bridges), because they are Layer 2 devices, forward broadcasts to all 
network segments, thus propagating broadcast storms. The best solution to the broadcast storm problem 
is to use a single broadcast address scheme on a network. In most modern IP implementations, you can 
set the address to be used as the broadcast address. Many implementations, including the one in the 
switch, support several addressing schemes for forwarding broadcast messages. 

Perform the tasks in these sections to enable these schemes:

By default, IP directed broadcasts are dropped; they are not forwarded. Dropping IP-directed broadcasts 
makes routers less susceptible to denial-of-service attacks. 

You can enable forwarding of IP-directed broadcasts on an interface where the broadcast becomes a 
physical (MAC-layer) broadcast. Only those protocols configured by using the ip forward-protocol 
global configuration command are forwarded. 

You can specify an access list to control which broadcasts are forwarded. When an access list is 
specified, only those IP packets permitted by the access list are eligible to be translated from directed 
broadcasts to physical broadcasts. For more information on access lists, see 

Beginning in privileged EXEC mode, follow these steps to enable forwarding of IP-directed broadcasts 
on an interface:

Enter global configuration mode.

interface interface-id

Enter interface configuration mode, and specify the interface to 
configure.