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6.7.3.4.1
IP Broadcast/Multicast Overview
When an IP packet needs to reach more then one unit, the destination address can be set to either a broad-
cast address or a multicast address.
BROADCAST - There are two types of IP broadcast address:
•
Directed broadcast
A directed broadcast address is an IP address where the host portion is all ones (for instance
172.30.1.255 is the directed broadcast address for the network 172.30.1.0/24, 172.30.1.207 is the
directed broadcast address for the network 172.30.1.192/24).
•
Limited broadcast
The limited broadcast address is 255.255.255.255.
Note:
Routing equipment (to prevent broadcast storms) do not by default forward limited broadcast
packets (255.255.255.255). On the other hand, directed broadcast packets are by default for-
warded because these packets are routable like any other unicast packets.
6.7.3.4.1.1
Broadcast
DIRECTED BROADCAST
Each interface of a unit has its own IP address and netmask. From the IP address and netmask, it is easy
to calculate the broadcast address associated to the interface. For instance, if the Ethernet interface ad-
dress of a HiPR-900 unit is 172.30.1.1/24 and the RF interface address is 10.0.1.2/24, then the broadcast
address of the Ethernet interface is 172.30.1.255 and the broadcast address of the RF interface is
10.0.1.255.
The "Directed Broadcast" radio buttons let the user select whether the unit must forward or not directed
broadcast packets. Upon reception of a directed broadcast packet, the unit takes the following actions:
If the directed broadcast address matches with one of the unit's interface broadcast address:
•
Keeps a copy for itself (passes to internal applications, if any).
•
If directed broadcast packets can be forwarded: Forwards the packet according to the routing table.
•
If directed broadcast packets cannot be forwarded: Silently discards the packet.
Note:
001-5099-000
Figure 53 - Broadcast Window Detail
53
HiPR-900 User Manual
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Troubleshooting
