162
Cisco Nexus 3548 Switch NX-OS Unicast Routing Command Reference
OL-27852-01
Chapter Unicast Routing Commands
ip directed-broadcast
ip directed-broadcast
To enable the translation of a directed broadcast to physical broadcasts, use the ip directed-broadcast
command. To disable this function, use the no form of this command.
ip directed-broadcast
no ip directed-broadcast
Syntax Description This command has no arguments or keywords.
Command Default Disabled; all IP directed broadcasts are dropped.
Command Modes Interface configuration mode
Subinterface configuration mode
Command History
Usage Guidelines An IP directed broadcast is an IP packet whose destination address is a valid broadcast address for some
IP subnet but which originates from a node that is not itself part of that destination subnet.
A device that is not directly connected to its destination subnet forwards an IP directed broadcast in the
same way it would forward unicast IP packets destined to a host on that subnet. When a directed
broadcast packet reaches a device that is directly connected to its destination subnet, that packet is
broadcast on the destination subnet. The destination address in the IP header of the packet is rewritten
to the configured IP broadcast address for the subnet, and the packet is sent as a link-layer broadcast.
If directed broadcast is enabled for an interface, incoming IP packets whose addresses identify them as
directed broadcasts intended for the subnet to which that interface is attached are broadcast on that
subnet.
If the no ip directed-broadcast command has been configured for an interface, directed broadcasts
destined for the subnet to which that interface is attached are dropped, rather than being broadcast.
Note Because directed broadcasts, and particularly Internet Control Message Protocol (ICMP) directed
broadcasts, have been abused by malicious persons, we recommend that you disable the ip
directed-broadcast command on any interface where directed broadcasts are not needed. We also
recommend that you use access lists to limit the number of broadcast packets.
This command requires the LAN Base Services license.
Examples This example shows how to enable forwarding of IP directed broadcasts on Ethernet interface 2/1:
switch# configure terminal
Release Modification
5.0(3)A1(1) This command was introduced.
To Next Page
Loading...
Need help?
General
