Ipv6 Unreachables - Allied Telesis AR2050V Command Reference Manual

IP 6 C
V OMMANDS
6
IPV UNREACHABLES

ipv6 unreachables

Overview Use this command to enable ICMPv6 (Internet Control Message Protocol version 6)
type 1, destination unreachable, messages.
Use the no variant of this command to disable destination unreachable messages.
This prevents an attacker from using these messages to discover the topology of a
network.
ipv6 unreachables
Syntax
no ipv6 unreachables
Default Destination unreachable messages are enabled by default.
Mode Global Configuration
Usage When a device receives a packet for a destination that is unreachable it returns an
ICMPv6 type 1 message. This message includes a reason code, as per the table
below. An attacker can use these messages to obtain information regarding the
topology of a network. Disabling destination unreachable messages, using the no
ipv6 unreachables command, secures your network against this type of probing.
NOTE
as traceroute, which depend on these messages to operate correctly.
Table 23-1: ICMPv6 type 1 reason codes and description
Example To disable destination unreachable messages, use the commands
awplus#
awplus(config)#
To enable destination unreachable messages, use the commands
awplus#
awplus(config)#
C613-50186-01 Rev B
: Disabling ICMPv6 destination unreachable messages breaks applications such
Code Description [RFC]
0 No route to destination [RFC4443]
1 Communication with destination administratively prohibited [RFC4443]
2 Beyond scope of source address [RFC4443]
3 Address unreachable [RF4443]
4 Port unreachable [RFC4443]
5 Source address failed ingress/egress policy [RFC4443]
6 Reject route to destination [RFC4443
7 Error in Source Routing Header [RFC6554]
configure terminal
no ipv6 unreachables
configure terminal
ipv6 unreachables
Command Reference for AR2050V
AlliedWare Plus™ Operating System - Version 5.4.7-1.x
783