Enabling sending ICMPv6 destination unreachable messages
If the device fails to forward a received IPv6 packet because of one of the following reasons, it drops the packet and sends a corresponding ICMPv6 Destination Unreachable error message to the source.
If no route is available for forwarding the packet, the device sends a "no route to destination" ICMPv6 error message to the source.
If the device fails to forward the packet because of an administrative prohibition (such as a firewall filter or an ACL), the device sends the source a "destination network administratively prohibited" ICMPv6 error message.
If the device fails to deliver the packet because the destination is beyond the scope of the source IPv6 address (for example, the source IPv6 address of the packet is a link-local address whereas the destination IPv6 address of the packet is a global unicast address), the device sends the source a "beyond scope of source address" ICMPv6 error message.
If the device fails to resolve the corresponding link layer address of the destination IPv6 address, the device sends the source an "address unreachable" ICMPv6 error message.
If the packet with the destination being local and transport layer protocol being UDP and the packet's destination port number does not match the running process, the device sends the source a "port unreachable" ICMPv6 error message.
If an attacker sends abnormal traffic that causes the device to generate ICMPv6 destination unreachable messages, end users may be affected. To prevent such attacks, you can disable the device from sending ICMPv6 destination unreachable messages.
To enable sending ICMPv6 destination unreachable messages:
Step | Command | Remarks |
---|---|---|
1. Enter system view. | system-view | N/A |
2. Enable sending ICMPv6 destination unreachable messages. | ipv6 unreachables enable | Disabled by default |