Enabling Sending Icmpv6 Time Exceeded Messages; Enabling Sending Icmpv6 Destination Unreachable Messages - HP 10500 Series Configuration Manual

multicast address, all the hosts in the multicast group send echo replies to Host B. To prevent such an
attack, disable a device from answering multicast echo requests by default. In some application
scenarios, however, you need to enable the device to answer multicast echo requests.
To enable replying to multicast echo requests:
Step
1. Enter system view.
2. Enable replying to multicast
echo requests.

Enabling sending ICMPv6 time exceeded messages

A device sends out an ICMPv6 Time Exceeded message in the following cases:
If a received IPv6 packet's destination IP address is not a local address and its hop limit is 1, the
•
device sends an ICMPv6 Hop Limit Exceeded message to the source.
• Upon receiving the first fragment of an IPv6 datagram with the destination IP address being the
local address, the device starts a timer. If the timer expires before all the fragments arrive, an
ICMPv6 Fragment Reassembly Timeout message is sent to the source.
If large quantities of malicious packets are received, the performance of a device degrades greatly
because it must send back ICMP Time Exceeded messages. You can disable sending of ICMPv6 Time
Exceeded messages.
To enable sending ICMPv6 time exceeded messages:
Step
1. Enter system view.
2. Enable sending ICMPv6 Time
Exceeded messages.

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.
Command
system-view
ipv6 icmpv6 multicast-echo-reply
enable
Command
system-view
ipv6 hoplimit-expires enable
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Remarks
N/A
Not enabled by default.
Remarks
N/A
Optional.
Enabled by default.