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Configuring Broadcast Settings

SecureStack B3 Configuration Guide 17-11

Configuring Broadcast Settings

Purpose

ToconfigureIPbroadcastsettings.Bydefault,interfacesontheSecureStackB3donotforward

broadcastpackets.

Commands

ip directed-broadcast

UsethiscommandtoenableordisableIPdirectedbroadcastsonaninterface.Bydefault,

interfacesontheSecureStackB3donotforwarddirectedbroadcasts.Thenoformofthis

commanddisablesIPdirectedbroadcastontheinterface.

Syntax

ip directed-broadcast

no ip directed-broadcast

Parameters

None.

Defaults

None.

Mode

Interfaceconfiguration:B3(su)‐>Router1(Config‐if(Vlan1))#

Usage

Directedbroadcastisanefficientmechanismforcommunicatingwithmultiplehostsonanetwork

whileonlytransmittingasingledatagram.Adirectedbroadcastisapacketsenttoallhostsona

specificnetworkorsubnet.Thedirectedbroadcastaddressincludesthenetworkorsubnetfields,

withthebinarybitsof

thehostportionoftheaddresssettoone.Forexample,foranetworkwith

theaddress192.168.0.0,thedirectedbroadcastaddresswouldbe192.168.255.25 5.Forasubnet

withtheaddress192.168.12.0,thedirectedbroadcastaddresswouldbe192.168.12.255.

InordertominimizebroadcastDoSattacks,forwardingofdirectedbroadcastsis

disabledby

defaultontheSecureStackB3,asrecommendedbyRFC2644.

Iftheabilitytosenddirectedbroadcaststoanetworkisrequired,youshouldenabledirected

broadcastsonlyontheoneinterfacethatwillbetransmittingthedatagrams.Forexample,ifa

SecureStackB3hasfiveroutedinterfacesfor

the10,20,30,40,and50networks,enablingdirected

broadcastonlyonthe30networkinterfacewillallowanyonefromanyothernetworks(10,20,40,

50)tosenddirectedbroadcasttothe30network.

For information about... Refer to page...

ip directed-broadcast 17-11

ip helper-address 17-12

Enterasys SecureStack B3 User Manual

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