H3C Technologies H3C WX3000E Series Wireless Switches - Manual (Page 106)

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• When forwarding a packet, if the MTU of the sending interface is smaller than the packet, but the
packet has been set as “Don't Fragment”, the device will send the source a “fragmentation needed
and Don't Fragment (DF)-set” ICMP error packet.
Disadvantages of sending ICMP error packets
Sending ICMP error packets facilitates network control and management, but it has the following
disadvantages:
• Increases network traffic.
• A device's performance degrades if it receives a lot of malicious packets that cause it to respond
with ICMP error packets.
• A host's performance degrades if the redirection function increases the size of its routing table.
• End users are affected because of receiving ICMP destination unreachable packets caused by
malicious users.
To prevent such problems, disable the device from sending ICMP error packets.
NOTE:
The switching engine on the WX3000E Series Wireless Switches does not support sending of ICMP error
packets.
Configuration procedure
Follow these steps to enable sending of ICMP error packets:
To do… Use the command… Remarks
Enter system view system-view —
Enable sending of ICMP timeout packets ip ttl-expires enable
Required
Disabled by default.
Enable sending of ICMP destination
unreachable packets
ip unreachables enable
Required
Disabled by default.
NOTE:
When sending ICMP timeout packets is disabled, the device will not send “TTL timeout” ICMP error
packets. However, “reassembly timeout” error packets will be sent normally.
Displaying and maintaining IP performance
optimization
To do… Use the command… Remarks
Display TCP connection statistics
display tcp statistics [ | { begin | exclude |
include } regular-expression ]
Available in any view
Display UDP statistics
display udp statistics [ | { begin | exclude |
include } regular-expression ]
Available in any view