Configuring the global unicast prefix and lifetime for hosts on a VLAN

These commands define the content of RAs transmitted on a VLAN.

Syntax:

ipv6 nd ra prefix <ipv6–prefix|prefix–len> <<valid–lifetime> <preferred–lifetime> | at <valid–date> <preferred–date> infinite | no–advertise> [no–autoconfig] [off–link]

no ipv6 nd ra prefix <ipv6–prefix|prefix–len> <<valid–lifetime> <preferred–lifetime> | at <valid–date> <preferred–date> infinite | no–advertise> [no–autoconfig] [off–link]

ipv6 nd ra prefix default <<valid–lifetime> <preferred–lifetime> | at <valid–date> <preferred–date> | infinite | no–advertise> [no–autoconfig] [off–link]

no ipv6 nd ra prefix default <<valid–lifetime> <preferred–lifetime> | at <valid–date> <preferred–date> | infinite | no–advertise> [no–autoconfig] [off–link]

Options for <valid–lifetime> <preferred–lifetime> :

Time in seconds:

[<0–4294967295> <0–4294967295>]

Specific date and time

[ at <valid–lifetime> <preferred–lifetime> ]

<valid–lifetime–MM/DD[/[YY]YY]]>

<valid–lifetime–HH:MM[:SS]>

<preferred–lifetime–MM/DD[/[YY]YY]]>

<preferred–lifetime–HH:MM[:SS]>]

<valid–date> <preferred–date>

VLAN-context command for specifying prefixes for the routing switch to include in RAs transmitted on the VLAN. IPv6 hosts use the prefixes in RAs to autoconfigure themselves with global unicast addresses. A host’s autoconfigured address is composed of the advertised prefix and the interface identifier in the host’s current link-local address.

valid–lifetime : The total time the prefix remains available before becoming unusable. After preferred-lifetime expiration, any autoconfigured address is deprecated and used only for transactions that began before the preferred-lifetime expired. If the valid lifetime also expires, the address becomes unusable. Default: 2,592,000 seconds–30 days; Range: 0–4294967295 seconds.

preferred–lifetime : The span of time during which the address can be freely used as a source and destination for traffic. This setting must be less than or equal to the corresponding valid–lifetime setting. Default: 604,000 seconds–7 days; Range: 0–4294967295 seconds

NOTE:

The valid and preferred lifetimes designated in this command are fixed values. Each successive transmission of the same RA contains the same valid and preferred lifetimes.

For more information on valid and preferred lifetimes, see Address lifetimes.

default : Applied to all on-link prefixes that are not individually set by theipv6 ra prefix <ipv6–prefix|prefix–len> command. It applies the same valid and preferred lifetimes, link state, autoconfiguration state, and advertise options to the advertisements sent for all on-link prefixes that are not individually configured with a unique lifetime. This also applies to the prefixes for any global unicast addresses configured later on the same VLAN.

Using default once, and then using it again with any new values results in the new values replacing the former values in advertisements.

If default is used without the no–advertise, no–autoconfig, or the off–link keyword, the advertisement setting for the absent keyword is returned to its default setting.

NOTE:

To configure a prefix as off–link or no–autoconfig, you must enter unique valid and preferred lifetimes with the prefix command (instead of the default command).

ipv6–prefix / prefix–len : Specifies the prefixes to advertise on the subject VLAN. A separate instance of the command must be used for each prefix to advertise.

infinite : Specifies that the prefix lifetime will not expire. This option sets the valid and preferred lifetimes to infinity. (All bits set to 1; ffffffff.)

no–advertise : Specifies no advertisement for the prefix. For example, if the routing-switches VLAN interface is configured with any prefixes that you do not want advertised on the VLAN, use this command to specify the prefixes to withhold from advertisements on the subject VLAN. Default: Advertising enabled.

no–autoconfig : Disables host autoconfiguration by turning off the A-bit in RAs. This requires hosts to acquire prefixes through manual or DHCPv6 assignments. Depending on the host implementation, a host that was previously configured by an RA to use autoconfiguration will not be affected by a later RA that includes no–autoconfig (unless the host disconnects and reconnects to the network). To re-enable host autoconfiguration (turn on the A-bit in RAs) for a given RA, use ipv6 nd ra prefix again, without invoking no–autoconfig. Default: A-bit turned on— host autoconfig turned on.

off–link : Sets the (L-bit) prefix information in an RA to indicate that the advertised prefix is not on the subject VLAN. A host that was previously configured using an RA without off–link will not be affected by a later RA that includes off–link (unless the host disconnects and reconnects to the network). Can be used in instances where the prefix is being deprecated, and you do not want any newly brought up hosts to use the prefix. Default: L-bit turned off.

The no form of the command deletes the specified prefix from RAs.