ADTRAN AOS Version R10.1.0 Command Reference Manual page 2501

Command Reference Guide
ip directed-broadcast
Use the ip directed-broadcast command to allow reception/forwarding of directed broadcasts. Use the no
form of this command to disable this feature. Variations of this command include:
ip directed-broadcast
ip directed-broadcast <name>
Syntax Description
<name>
Default Values
By default, this command is disabled.
Command History
Release 14.1
Functional Notes
A directed broadcast is a packet intended for all nodes on a nonlocal network. For example, the broadcast
address 255.255.255.255 reaches all nodes on a network; the directed broadcast address 128.1.255.255
is intended for all nodes whose network address is 128.1.0.0. A router not directly attached to 128.1.0.0
simply forwards the directed broadcast packet to the next hop. A router on network 128.1.0.0 that has ip
directed-broadcast enabled, accepts and forwards the packet to all nodes whose network address is
128.1.0.0. Routers connecting subnets of 128.1.0.0 also accept and forward the packet to the nodes on
their respective subnets. When a directed broadcast packet reaches a router that is directly connected to
its destination subnet, that packet is distributed as a broadcast on the destination subnet. The packet is
then sent as a link-layer broadcast.
The ip directed-broadcast command controls the distribution of directed broadcasts when they reach
their target subnets. Only the final transmission of the directed broadcast on its ultimate destination subnet
is affected. It does not affect the transit unicast routing of IP directed broadcasts.
If ip directed-broadcast is enabled for this interface, incoming IP packets whose addresses identify them
as directed broadcasts intended for the subnet to which this interface is attached will be forwarded as
broadcasts on that subnet. Forwarding of the packets can be limited by specifying an ACL with this
command. In this case, only directed broadcasts that are permitted by the specified ACL will be forwarded,
and all other directed broadcasts directed to this interface subnet will be dropped.
Disabling the ip directed-broadcast command will cause directed broadcasts destined for the subnet to
which this interface is attached to be dropped.
This option is a requirement for routers as described in RFC 1812, section 4.2.2.11. Furthermore, it is
disabled by default (RFC 2644), with the intended goal of reducing the efficacy of certain types of denial of
service (DoS) attacks.
60000CRG0-35E
Specifies IP access control list (ACL) name.
Command was introduced.
Copyright © 2012 ADTRAN, Inc.
PPP Interface Command Set
2501