H3C MSR 2600 Configuration Manual page 181

The selected route is not created or modified by any ICMP redirect packet.
The selected route is not destined for 0.0.0.0.
There is no source route option in the received packet.
ICMP redirect packets simplify host management and enable hosts to gradually optimize their
routing table.
• ICMP time-exceeded packets
A device sends ICMP time-exceeded packets by following these rules:
If a received packet is not destined for the device and the TTL field of the packet is 1, the device
sends an ICMP TTL Expired in Transit packet to the source.
When the device receives the first fragment of an IP datagram destined for it, it starts a timer. If
the timer expires before all the fragments of the datagram are received, the device sends an
ICMP Fragment Reassembly Timeout packet to the source.
ICMP destination unreachable packets
•
A device sends ICMP destination unreachable packets by following these rules:
If a packet does not match any route and there is no default route in the routing table, the device
sends a Network Unreachable ICMP error packet to the source.
If a packet is destined for the device but the transport layer protocol of the packet is not
supported by the device, the device sends a Protocol Unreachable ICMP error packet to the
source.
NOTE:
If a DHCP enabled device receives an ICMP echo reply without sending any ICMP echo requests,
the device does not send any ICMP Protocol Unreachable messages to the source. For more
information about DHCP, see
If a UDP packet is destined for the device but the packet's port number does not match the
corresponding process, the device sends the source a Port Unreachable ICMP error packet.
If the source uses Strict Source Routing to send packets, but the intermediate device finds that the
next hop specified by the source is not directly connected, the device sends the source a Source
Routing Failure ICMP error packet.
If the MTU of the sending interface is smaller than the packet and the packet has DF set, the
device sends the source a Fragmentation Needed and DF-set ICMP error packet.
To enable sending ICMP error packets:
Step
1. Enter system view.
2. Enable sending ICMP
error packets.
Layer 3—IP Services Configuration Guide
Command
system-view
•
Enable sending ICMP redirect packets:
ip redirects enable
•
Enable sending ICMP time-exceeded
packets:
ip ttl-expires enable
•
Enable sending ICMP destination
unreachable packets:
ip unreachables enable
166
.
Remarks
N/A
The default settings are
disabled.