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Catalyst 3550 Multilayer Switch Software Configuration Guide
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Chapter 22 Configuring IP Unicast Routing
Configuring IP Addressing
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 Dynamic Host
Configuration Protocol (DHCP) information.
Beginning in privileged EXEC mode, follow these steps to enable forwarding UDP broadcast packets
on an interface and specify the destination address:
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.
Command Purpose
Step 1
configure terminal Enter global configuration mode.
Step 2
interface interface-id Enter interface configuration mode, and specify the Layer 3 interface
to configure.
Step 3
ip helper-address address Enable forwarding and specify the destination address for forwarding
UDP broadcast packets, including BOOTP.
Step 4
exit Return to global configuration mode.
Step 5
ip forward-protocol {udp [port] | nd | sdns} Specify which protocols the router forwards when forwarding
broadcast packets.
• udp—Forward UDP datagrams.
port: (Optional) Destination port that controls which UDP
services are forwarded.
• nd—Forward ND datagrams.
• sdns—Forward SDNS datagrams
Step 6
end Return to privileged EXEC mode.
Step 7
show ip interface [interface-id]
or
show running-config
Verify the configuration on the interface or all interfaces.
Step 8
copy running-config startup-config (Optional) Save your entries in the configuration file.