HP VPN Firewall Appliances Network Management Configuration Guide

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Configuring the maximum ICMPv6 error packets sent in an
interval
If too many ICMPv6 error packets are sent within a short period of time in a network, network congestion
might occur. To avoid network congestion, you can control the maximum number of ICMPv6 error
packets sent within a specific time by adopting the token bucket algorithm.
You can set the capacity of a token bucket to determine the number of tokens in the bucket. In addition,
you can set the update interval of the token bucket, that is, the interval for restoring the configured
capacity. One token allows one ICMPv6 error packet to be sent. Each time an ICMPv6 error packet is
sent, the number of tokens in a token bucket decreases by one. If the number of ICMPv6 error packets
successively sent exceeds the capacity of the token bucket, the additional ICMPv6 error packets cannot
be sent out until the capacity of the token bucket is restored.
To configure the capacity and update interval of the token bucket:
Ste
p
Command Remarks
1. Enter system view.
system-view N/A
2. Configure the
capacity and update
interval of the token
bucket.
ipv6 icmp-error { bucket
bucket-size | ratelimit
interval } *
Optional.
By default, the capacity of a token bucket is 10 and
the update interval is 100 milliseconds. A
maximum of 10 ICMPv6 error packets can be sent
within 100 milliseconds.
The update interval "0" indicates that the number
of ICMPv6 error packets sent is not restricted.
Enabling replying to multicast echo requests
If hosts are configured to answer multicast echo requests, an attacker might use this mechanism to attack
a host. For example, if Host A (an attacker) sends an echo request with the source being Host B to a
multicast address, all 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:
Ste
p
Command Remarks
1. Enter system view.
system-view N/A
2. Enable replying to multicast
echo requests.
ipv6 icmpv6 multicast-echo-reply
enable
The device is disabled from
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.