Enterasys b5

Configuring Broadcast Settings
19-12 IP Configuration
Configuring Broadcast Settings
Purpose
ToconfigureIPbroadcastsettings.Bydefault,interfacesontheEnterasysB5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EnterasysB5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:B5(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192.168.0.0/16,thedirectedbroadcastaddresswouldbe192.168.255.255.Forasubnet
withtheaddress192.168.12.0/24,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EnterasysB5,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
EnterasysB5hasfiveroutedinterfacesfor
the10,20,30,40,and50networks,enablingdirected
For information about... Refer to page...
ip directed-broadcast 19-12
ip forward-protocol 19-13
ip helper-address 19-14