Broadcast Addressing - Juniper IGP - CONFIGURATION GUIDE V11.1.X Configuration Manual

Broadcast Addressing

A broadcast is a data packet destined for all hosts on a particular physical network.
Network hosts recognize broadcasts by special addresses.
The router supports the following kinds of broadcast types:
Several early IP implementations do not use the current broadcast address standard.
Instead, they use the old standard, which calls for all zeros instead of all ones to
indicate broadcast addresses. Many of these implementations do not recognize a
broadcast address of all ones and fail to respond to the broadcast correctly. Others
forward broadcasts of all ones, which causes a serious network overload known as
a broadcast storm. Implementations that exhibit these problems include systems
based on versions of BSD UNIX before version 4.3.
Routers provide some protection from broadcast storms by limiting their extent to
the local cable. Bridges (including intelligent bridges), because they are layer 2 devices,
forward broadcasts to all network segments, thus propagating all broadcast storms.
ipAddress, interfaceType and interfaceSpecifier (as indicated in Interface Types
and Specifiers in JUNOSe Command Reference Guide ), and an optional MAC
address
You can issue this command only for an IP Ethernet-based interface.
For subscriber interface configurations, the IP address–MAC address pair must
have a matching source prefix that already exists on the subscriber interface. If
the matching source prefix does not exist, the IP–MAC address pair is rejected.
See Configuring Subscriber Interfaces in the JUNOSe Broadband Access Configuration
Guide for information about using subscriber interfaces.
Example 1 Packets originating from host 192.56.20.1 and validated at Gigabit
Ethernet interface with the MAC address 0090.1a00.0170
host1(config)#arp 192.56.20.1 gig 2/0 0090.1a00.0170 validate
Example 2 Subscriber interface MAC address validation enabled
host1(config)#arp 192.168.32.0 ip subsc1 000.0001.8100
Use the no version to remove an entry from the ARP cache.
See arp
Limited broadcast A packet is sent to a specific network or series of networks.
A limited broadcast address includes the network or subnet fields. In a limited
broadcast packet destined for a local network, the network identifier portion and
host identifier portion of the destination address is either all ones
(255.255.255.255) or all zeros (0.0.0.0).
Flooded broadcast A packet is sent to every network.
Directed broadcast A packet is sent to a specific destination address where
only the host portion of the IP address is either all ones or all zeros (such as
192.20.255.255 or 190.20.0.0).
Chapter 1: Configuring IP
23
Broadcast Addressing