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Understanding IP Directed Broadcast for J-EX Series Switches
IP directed broadcast helps you implement remote administration tasks such as backups
and wake-on-LAN (WOL) application tasks by sending broadcast packets targeted at
the hosts in a specified destination subnet. IP directed broadcast packets traverse the
network in the same way as unicast IP packets until they reach the destination subnet.
When they reach the destination subnet and IP directed broadcast is enabled on the
receiving switch, the switch translates (“explodes”) the IP directed broadcast packet
into a broadcast that floods the packet on the target subnet. All hosts on the target
subnet receive the IP directed broadcast packet.
This topic covers:
•
IP Directed Broadcast for J-EX Series Switches Overview on page 876
•
IP Directed Broadcast Implementation for J-EX Series Switches on page 876
•
When to Enable IP Directed Broadcast on page 877
•
When Not to Enable IP Directed Broadcast on page 877
IP Directed Broadcast for J-EX Series Switches Overview
IP directed broadcast packets have a destination IP address that is a valid broadcast
address for the subnet that is the target of the directed broadcast (the target subnet).
The intent of an IP directed broadcast is to flood the target subnet with the broadcast
packets without broadcasting to the entire network. IP directed broadcast packets cannot
originate from the target subnet.
When you send an IP directed broadcast packet, as it travels to the target subnet, the
network forwards it in the same way as it forwards a unicast packet. When the packet
reaches a switch that is directly connected to the target subnet, the switch checks to see
whether IP directed broadcast is enabled on the interface that is directly connected to
the target subnet:
•
If IP directed broadcast is enabled on that interface, the switch broadcasts the packet
on that subnet by rewriting the destination IP address as the configured broadcast IP
address for the subnet. The switch converts the packet to a link-layer broadcast packet
that every host on the network processes.
•
If IP directed broadcast is disabled on the interface that is directly connected to the
target subnet, the switch drops the packet.
IP Directed Broadcast Implementation for J-EX Series Switches
You configure IP directed broadcast on a per-subnet basis by enabling IP directed
broadcast on the Layer 3 interface of the subnet’s VLAN. When the switch that is
connected to that subnet receives a packet that has the subnet’s broadcast IP address
as the destination address, the switch broadcasts the packet to all hosts on the subnet.
By default, IP directed broadcast is disabled.
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Dell PowerConnect J-Series Ethernet Switch Complete Software Guide for Junos OS
Summary of Contents for PowerConnect J-EX8208
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Page 383: ...CHAPTER 21 Configuration Statements for Power Management 311 ...
Page 387: ...CHAPTER 22 Operational Mode Commands for Power Management 315 ...
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Page 581: ...CHAPTER 38 Operational Mode Commands for System Services 509 ...
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Page 631: ...CHAPTER 41 Configuration Statements for System Monitoring 559 ...
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Page 683: ...CHAPTER 42 Operational Mode Commands for System Monitoring 611 ...
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Page 1061: ...CHAPTER 56 Operational Mode Commands for Interfaces 989 ...
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Page 1297: ...CHAPTER 63 Operational Mode Commands for Bridging and VLANs 1225 ...
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Page 1461: ...CHAPTER 69 Operational Mode Commands for Spanning Tree Protocols 1389 ...
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Page 1819: ...CHAPTER 74 Operational Commands for Layer 3 Protocols 1747 ...
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Page 2215: ...CHAPTER 80 Operational Mode Commands for IGMP Snooping and Multicast 2143 ...
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