R21xx-HP FlexFabric 11900 Layer 3 IP Services Command Reference

145
Views
System view
Predefined user roles
network-admin
Usage guidelines
Disable forwarding of ICMP fragments can prevent ICMP fragment attacks.
Examples
# Disable forwarding of ICMP fragments.
<Sysname> system-view
[Sysname] ip icmp fragment discarding
ip mtu
Use ip mtu to configure an MTU for an interface.
Use undo ip mtu to restore the default.
Syntax
ip mtu mtu-size
undo ip mtu
Default
No MTU is configured for an interface.
Views
Interface view
Predefined user roles
network-admin
Parameters
mtu-size: Specifies an MTU in the range of 128 to 2000 bytes.
Usage guidelines
Set an appropriate MTU to avoid fragmentation. The MTU for the interface applies to only packets that
are sent to the CPU for forwarding by software, for example, the packets that are sourced from or
destined to the interface.
When a packet exceeds the MTU of the output interface, the device processes it in one of the following
ways:
• If the packet disallows fragmentation, the device discards it.
• If the packet allows fragmentation, the device fragments it and forwards the fragments.
Fragmentation and reassembling consume system resources, so set an appropriate MTU for an interface
to avoid fragmentation.