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Cisco Catalyst 3750-X User Manual

Cisco Catalyst 3750-X
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42-15
Catalyst 3750-X and 3560-X Switch Software Configuration Guide
OL-21521-01
Chapter 42 Configuring IP Unicast Routing
Configuring IP Addressing
Enabling Directed Broadcast-to-Physical Broadcast Translation
By default, IP directed broadcasts are dropped; they are not forwarded. Dropping IP-directed broadcasts
makes routers less susceptible to denial-of-service attacks.
You can enable forwarding of IP-directed broadcasts on an interf
ace where the broadcast becomes a
physical (MAC-layer) broadcast. Only those protocols configured by using the ip forward-protocol
global configuration command are forwarded.
You can specify an access list to control which broadc
asts are forwarded. When an access list is
specified, only those IP packets permitted by the access list are eligible to be translated from directed
broadcasts to physical broadcasts. For more information on access lists, see Chapter 37, “Configuring
Network Security with ACLs.
Beginning in privileged EXEC mode, follow these steps t
o enable forwarding of IP-directed broadcasts
on an interface:
Use the no ip dir
ected-broadcast interface configuration command to disable translation of directed
broadcast to physical broadcasts. 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 interface to
configure.
Step 3
ip directed-broadcast [access-list-number] Enable directed broadcast-to-physical broadcast translation on the
interface. You can include an access list to control which broadcasts
are forwarded. When an access list, only IP packets permitted by the
access list can be translated
Note The ip directed-broadcast interface configuration command
can be configured on a VPN routing/forwarding(VRF)
interface and is VRF aware. Directed broadcast traffic is
routed only within the VRF.
Step 4
exit Return to global configuration mode.
Step 5
ip forward-protocol {udp [port] | nd | sdns} Specify which protocols and ports the router forwards when
forwarding broadcast packets.
udp—Forward UPD 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.

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Cisco Catalyst 3750-X Specifications

General IconGeneral
Switching Capacity160 Gbps
Stacking Bandwidth64 Gbps
Max Stacking Units9
Layer SupportLayer 2 and Layer 3
Form FactorRack-mountable
DRAM256 MB
Flash Memory64 MB
ModelCisco Catalyst 3750-X Series
Ports24 or 48 10/100/1000 Ethernet ports
Uplink Interfaces4 SFP or 2 SFP+
FeaturesStackWise Plus, EnergyWise
ImageIP Base or IP Services
Operating Temperature0 to 40°C
Operating Humidity10 to 85% noncondensing

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