H3C Technologies H3C S12500-X Series Switches - Manual (Page 108)

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Optimizing IP performance
A customized configuration can help optimize overall IP performance. This chapter describes various
techniques you can use to customize your installation.
Enabling an interface to receive and forward
directed broadcasts destined for the directly
connected network
A directed broadcast packet is destined for all hosts on a specific network. In the destination IP address
of the directed broadcast, the network ID identifies the target network, and the host ID is made up of all
ones.
If an interface is allowed to forward directed broadcasts destined for the directly connected network,
hackers can exploit this vulnerability to attack the target network. In some scenarios, however, an
interface must receive and forward such directed broadcast packets to support UDP helper.
This task enables an interface to accept directed broadcast packets that are destined for and received
from the directly connected network to support UDP helper, which converts the directed broadcasts to
unicasts and forwards them to a specific server.
Configuration procedure
To enable an interface to receive and forward directed broadcasts destined to the directly connected
network:
Step Command Remarks
1. Enter system view. system-view N/A
2. Enter interface view.
interface interface-type
interface-number
N/A
3. Enable the interface to receive
and forward directed
broadcasts destined for the
directly connected network.
ip forward-broadcast
By default, an interface cannot
receive or forward directed
broadcasts destined for the directly
connected network.
Configuration example
Network requirements
As shown in Figure 42 , the default gateway of the host is the IP address 1.1.1.2/24 of VLAN-interface 3
of the switch.
Enable VLAN-interface 2 to forward directed broadcasts destined for the directly connected network.
The server can receive directed broadcasts from the host to IP address 2.2.2.255.