3Com Switch 7750 Configuration Guide

Disabling ICMP Error Message Sending 133
If you reference an ACL to filter directed broadcasts, only the directed broadcasts
that pass the ACL filtering can be forwarded to the directly connected network.
Disabling ICMP Error
Message Sending
Sending error packets is the major function of the Internet Control Message
Protocol (ICMP). ICMP packets are usually sent by the network layer protocols or
transport layer protocols to notify corresponding devices of failures.
Although sending ICMP error packets facilitates network control and
management, it still has the following disadvantages:
■ Sending a lot of ICMP packets will increase network traffic.
■ If receiving a lot of malicious packets that cause a device to send ICMP error
packets, the device’s performance will be reduced.
■ As the ICMP redirection function increases the routing table size of hosts, the
hosts’ performance will be reduced if the routing table becomes very large.
■ If a host sends malicious ICMP destination unreachable packets, end users may
be affected.
To solve such problems, you can disable a device from sending ICMP error packets.
Currently, you can only disable the sending of ICMP redirect messages.
Displaying and
Debugging IP
Performance
After the above configurations, you can execute the display command in any
view to display the running status to verify your IP performance configuration.
Table 79 Enable forwarding of directed broadcast packets
Operation Command Description
Enter system view system-view -
Enter VLAN interface view interface interface-type
interface-number
-
Enable forwarding of
directed broadcast packets
to a directly connected
network
ip forward-broadcast
[ acl-number ]
Required
By default, the switch does not
forward directed broadcast packets
to a directly connected network.
Table 80 Disable ICMP redirect message sending
Operation Command Description
Enter system view system-view -
Disable ICMP redirect
message sending
undo icmp redirect send Required
By default, the ICMP redirect
message sending is enabled.