IPv6 Configuration Guide K/KA/KB.15.15

12 IPv6 Diagnostic and Troubleshooting
NOTE: All commands previously in the Summary of commands table are indexed under the entry
Command syntax.
Introduction
The IPv6 ICMP feature enables control over the error and informational message rate for IPv6
traffic, which can help mitigate the effects of a Denialof- service attack. Ping6 enables verification
of access to a specific IPv6 device, and traceroute6 enables tracing the route to an IPv6-enabled
device on the network.
ICMP Rate-Limiting
ICMP rate-limiting controls the rate at which ICMPv6 generates error and informational messages
for features such as:
• neighbor solicitations
• neighbor advertisements
• multicast listener discovery (MLD)
• path MTU discovery (PMTU)
• duplicate address discovery (DAD)
• neighbor unreachability detection (NUD)
• router discovery
• neighbor discovery (NDP)
ICMPv6 error message generation is enabled by default. The rate of message generation can be
adjusted, or message generation can be disabled.
Controlling the frequency of ICMPv6 error messages can help to prevent DoS (Denial- of- Service)
attacks. With IPv6 enabled on the switch, you can control the allowable frequency of these messages
with ICMPv6 rate-limiting.
Syntax
ipv6 icmp error-interval 0 - 2147483647 [ bucket-size 1 - 200 ]
no ipv6 icmp error-interval
This command is executed from the global configuration level, and uses a “token
bucket” method for limiting the rate of ICMP error and informational messages.
Using this method, each ICMP message uses one token, and a message can be
sent only if there is a token available. In the default configuration, a new token can
be added every 100 milliseconds, and a maximum of 10 tokens are allowed in
the token bucket. If the token bucket is full, a new token cannot be added until an
existing token is used to enable sending an ICMP message. You can increase or
decrease both the the frequency with which used tokens can be replaced and
(optionally) the number of tokens allowed to exist.
error-interval
Specifies the time interval in milliseconds between successive token adds.
Increasing this value decreases the rate at which tokens can be added. A setting
of 0 disables ICMP messaging.
Default : 100; Range: 0 - 2147483647
Introduction 277