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Cisco ASA 5500 Series Configuration Guide using ASDM
OL-20339-01
Chapter 25 Configuring IPv6 Neighbor Discovery
Configuring Router Advertisement Messages
Additional Guidelines and Limitations
A date can be set to specify the expiration of a prefix. The valid and preferred lifetimes are counted down
in real time. When the expiration date is reached, the prefix will no longer be advertised.
When onlink is on (by default), the specified prefix is assigned to the link. Nodes sending traffic to such
addresses that contain the specified prefix consider the destination to be locally reachable on the link.
When autoconfig is on (by default), it indicates to hosts on the local link that the specified prefix can be
used for IPv6 autoconfiguration.
For stateless autoconfiguration to work correctly, the advertised prefix length in router advertisement
messages must always be 64 bits.
Default Settings for IPv6 Prefixes
Table 25-9 lists the default settings for neighbor reachable time parameters.
Configuring IPv6 Prefixes
To configure IPv6 prefixes on an interface, perform the following steps:
Step 1 In the Interface IPv6 Prefixes area, click Add.
The Add IPv6 Prefix for Interface dialog box appears.
Step 2 Enter the IPv6 address with the prefix length.
Step 3 (Optional) To configure the IPv6 address manually, check the No Auto-Configuration check box. This
setting indicates to hosts on the local link that the specified prefix cannot be used for IPv6
autoconfiguration.
Step 4 (Optional) To indicate that the IPv6 prefix is not advertised, check the No Advertisements check box.
Step 5 (Optional) The Off Link check box indicates that the specified prefix is assigned to the link. Nodes
sending traffic to addresses that contain the specified prefix consider the destination to be locally
reachable on the link. This prefix should not be used for on-link determination.
Step 6 In the Prefix Lifetime area, click the Lifetime Duration radio button, and specify the following:
a. A valid lifetime for the prefix in seconds from the drop-down list. This setting is the amount of time
that the specified IPv6 prefix is advertised as being valid. The maximum value represents infinity.
Valid values are from 0 to 4294967295. The default is 2592000 (30 days).
Table 25-9 Default for IPv6 Prefixes Parameters
Parameters Default
prefix lifetime The default lifetime is 2592000 seconds (30 days)
and a preferred lifetime is 604800 seconds (7
days).
on-link flag The flag is on by default, which means that the
prefix is used on the advertising interface.
autoconfig flag The flag is on by default, which means that the
prefix is used for autoconfiguration.
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