Establishing An Ip Broadcast Address; Flooding Ip Broadcasts - Cisco 3845 - Security Bundle Router Software Manual

Configuring IP Addressing
Command
Step 4
exit
Step 5
ip forward-protocol {udp [port] | nd | sdns} Specify which protocols the router forwards when forwarding
Step 6
end
Step 7
show ip interface [interface-id]
or
show running-config
Step 8
copy running-config startup-config
Use the no ip helper-address interface configuration command to disable the forwarding of broadcast
packets to specific addresses. Use the no ip forward-protocol global configuration command to remove
a protocol or port.

Establishing an IP Broadcast Address

The most popular IP broadcast address (and the default) is an address consisting of all ones
(255.255.255.255). However, the switch can be configured to generate any form of IP broadcast address.
Beginning in privileged EXEC mode, follow these steps to set the IP broadcast address on an interface:
Command
Step 1
configure terminal
Step 2
interface interface-id
Step 3 ip broadcast-address ip-address
Step 4
end
Step 5
show ip interface [interface-id]
Step 6
copy running-config startup-config
To restore the default IP broadcast address, use the no ip broadcast-address interface configuration
command.

Flooding IP Broadcasts

You can allow IP broadcasts to be flooded throughout your internetwork in a controlled fashion by using
the database created by the bridging STP. Using this feature also prevents loops. To support this
capability, bridging must be configured on each interface that is to participate in the flooding. If bridging
is not configured on an interface, the interface can receive broadcasts but it never forwards the broadcasts
it receives, and the router never uses that interface to send broadcasts received on a different interface.
Packets that are forwarded to a single network address using the IP helper-address mechanism can be
flooded. Only one copy of the packet is sent on each network segment.
Cisco ME 3800X and 3600X Switch Software Configuration Guide
29-14
Purpose
Return to global configuration mode.
broadcast packets.
Return to privileged EXEC mode.
Verify the configuration on the interface or all interfaces.
(Optional) Save your entries in the configuration file.
Purpose
Enter global configuration mode.
Enter interface configuration mode, and specify the interface to
configure.
Enter a broadcast address different from the default, for example
128.1.255.255.
Return to privileged EXEC mode.
Verify the broadcast address on the interface or all interfaces.
(Optional) Save your entries in the configuration file.
Chapter 29 Configuring IP Unicast Routing
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