ip unreachables enable

Use ip unreachables enable to enable sending ICMP destination unreachable messages.

Use undo ip unreachables enable to disable sending ICMP destination unreachable messages.

Syntax

ip unreachables enable

undo ip unreachables enable

Default

Sending ICMP destination unreachable messages is disabled.

Views

System view

Predefined user roles

network-admin

Usage guidelines

A device sends ICMP destination unreachable messages 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 message 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 message to the source.

• If a UDP packet is destined for the device but the packet's port number does not match the running process, the device sends the source a Port Unreachable ICMP error message.

• 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 message.

• If the MTU of the sending interface is smaller than the packet and the packet has a Don't Fragment set, the device sends the source a Fragmentation Needed and Don't Fragment-Set ICMP error message.

Examples

# Enable sending ICMP destination unreachable messages.

<Sysname> system-view
[Sysname] ip unreachables enable