Establishing An Ip Broadcast Address - Cisco WS-C3020 Software Configuration Manual

Configuring IP Addressing
By default, both UDP and ND forwarding are enabled if a helper address has been defined for an
interface. The description for the ip forward-protocol interface configuration command in the Cisco
IOS IP Command Reference, Volume 1 of 3: Addressing and Services, Release 12.2 lists the ports that
are forwarded by default if you do not specify any UDP ports.
If you do not specify any UDP ports when you configure the forwarding of UDP broadcasts, you are
configuring the router to act as a BOOTP forwarding agent. BOOTP packets carry DHCP information.
Beginning in privileged EXEC mode, follow these steps to enable forwarding UDP broadcast packets on
an interface and specify the destination address:
Command
Step 1 configure terminal
Step 2
interface interface-id
Step 3
ip helper-address address
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
Cisco Catalyst Blade Switch 3020 for HP Software Configuration Guide
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Purpose
Enter global configuration mode.
Enter interface configuration mode, and specify the Layer 3 interface
to configure.
Enable forwarding and specify the destination address for forwarding
UDP broadcast packets, including BOOTP.
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 34 Configuring IP Unicast Routing
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