ipv6 nd ra prefix

Syntax

ipv6 nd ra prefix ipv6-prefix/prefix-len

no ipv6 nd ra prefix ipv6-prefix/prefix-len

[valid-lifetime preferred-lifetime|at|valid-date preferred-date|infinite|at|no-advertise]

[no-autoconfig]

[off-link]

Syntax

ipv6 nd ra prefix default

no ipv6 nd ra prefix default

[valid-lifetime preferred-lifetime|at|valid-date preferred-date|infinite|at|no-advertise]

[no-autoconfig]

[off-link]

Options

Options for valid-lifetime preferred-lifetime :

Time in seconds:

[0 - 4294967295|0 - 4294967295]

Specific date and time

valid-lifetime preferred-lifetime

valid-lifetime-MM/DD/YY

valid-lifetime-HH:MM:SS

preferred-lifetime-MM/DD/YY

preferred-lifetime-HH:MM:SS

at valid-date preferred-date

valid-date - MM/DD/[YY]YY]

valid-date - HH:MM[:SS}

preferred-date - MM/DD/[YY]YY

preferred-date - HH:MM[:SS}

VLAN or tunnel context command for specifying prefixes for the routing switch to include in RAs transmitted on the VLAN or tunnel. 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 second – 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.

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 or tunnel.

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 or tunnel. 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 or tunnel 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 or tunnel.

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.

Using the default command to configure prefix advertisement content

The table lists the global unicast addresses configured on a VLAN, with original and updated settings configured using the default command.
Example using the default command to configure prefix advertisement content

Address or prefix

Interface

Original lifetime & autoconfig

Updated lifetime & autoconfig

Advertise on VLAN 100?

2001:db8:0:f::f1/64

VLAN 100

15 days

14 days

Auto: Yes

30 days

25 days

Auto: No

Yes

2001:db8:0:b::b1/64

VLAN 100

2001:db8:0:c::c1/64

VLAN 100

2001:db8:0:d::d1/64

VLAN 100

2001:db8:0:a::/64

Off-Link

12/31/2010at 00:00:01 12/20/2010at 00:00:01 Auto: Yes

not updated

Example output

Using the default command to configure and update prefix advertisements 

Switch(config)# vlan 100
Switch(vlan-100)# ipv6 address 2001:db8:0:f::f1/64
Switch(vlan-100)# ipv6 address 2001:db8:0:b::b1/64 1
Switch(vlan-100)# ipv6 address 2001:db8:0:c::c1/64
Switch(vlan-100)# ipv6 nd ra prefix default 1296000 1209600 2
Switch(vlan-100)# show ipv6 nd ra prefix vlan 100

 IPv6 Neighbor Discovery Prefix Information

 VLAN Name : VLAN100 3

   IPv6 Prefix        : Default
   Valid Lifetime     : 15 days
   Preferred Lifetime : 14 days
   On-link Flag       : On
   Autonomous Flag    : On
   Advertise Flag     : On

Switch(vlan-100)# ipv6 address 2001:db8:0:d::d1/64 4
Switch(vlan-100)# ipv6 nd ra prefix 2001:db8:0:d::/64 infinite no-autoconfig
Switch(vlan-100)# ipv6 nd ra prefix 2001:db8:0:a::/64 at 12/31/2010 00:00:01 12/20/2010 00:00:01 
                  off-link 5
Switch(vlan-100)# show ipv6 nd ra prefix vlan 100

 IPv6 Neighbor Discovery Prefix Information

 VLAN Name : VLAN100

   IPv6 Prefix        : Default 6
   Valid Lifetime     : 15 days
   Preferred Lifetime : 14 days
   On-link Flag       : On
   Autonomous Flag    : On
   Advertise Flag     : On

   IPv6 Prefix        : 2001:db8:0:a::/64 7
   Valid Lifetime     : 12/31/2010 00:00:01
   Preferred Lifetime : 12/20/2010 00:00:01
   On-link Flag       : Off
   Autonomous Flag    : On
   Advertise Flag     : On

   IPv6 Prefix        : 2001:db8:0:d::/64 8
   Valid Lifetime     : Infinite
   Preferred Lifetime : Infinite
   On-link Flag       : On
   Autonomous Flag    : Off
   Advertise Flag     : On

Switch(vlan-100)# ipv6 nd ra prefix default 2592000 2160000 no-autoconfig 9
Switch(vlan-100)# show ipv6 nd ra prefix vlan 100

 IPv6 Neighbor Discovery Prefix Information

 VLAN Name : VLAN100

   IPv6 Prefix        : Default 10
   Valid Lifetime     : 30 days
   Preferred Lifetime : 25 days
   On-link Flag       : On
   Autonomous Flag    : Off
   Advertise Flag     : On

   IPv6 Prefix        : 2001:db8:0:a::/64 11
   Valid Lifetime     : 12/31/2010 00:00:01
   Preferred Lifetime : 12/20/2010 00:00:01
   On-link Flag       : Off
   Autonomous Flag    : On
   Advertise Flag     : On

   IPv6 Prefix        : 2001:db8:0:d::/64 12
   Valid Lifetime     : Infinite
   Preferred Lifetime : Infinite
   On-link Flag       : On
   Autonomous Flag    : Off
   Advertise Flag     : On

1 Global unicast addresses configured on VLAN 100

2 To enable advertising prefixes of global unicast addresses configured on the VLAN: The default command sets default lifetime, prefix link status (on or off-link), autoconfiguration (Autonomous Flag) status (on or off), and advertisement setting (on or off).

3 Show command displays default prefix mode settings for global unicast addresses configured on VLAN 100.

4 New global unicast address configured on the VLAN. Followed by command to assign unique lifetime and autoconfig setting in the advertisements for this prefix. Link flag and Advertise flag omitted from the command and therefore set to "On" by default.

5 Off-link prefix designated with unique lifetime. Autoconfig (Autonomous) flag and Advertise flag omitted from the command and therefore set to "On".

6 Show command displays default advertisement settings for prefixes of global unicast addresses configured on VLAN 100.

7 Show command displays unique advertisement settings for 2001:db8:0:a::/64 also configured on VLAN 100.

8 Show command displays unique advertisement settings for 2001:db8:0:d::/64 identified as an off-link prefix.

9 For prefixes configured on the VLAN and not specifically addressed by a prefix command, default changes the default lifetime and the autoconfig setting in advertisements for these prefixes. On-Link flag and Advertise flag omitted from the command and therefore set to "On" by default.

10 Show command displays changes in default prefix mode settings for global unicast addresses configured on VLAN 100.

11 No change for the on-link prefix specifically configured by a prefix command, and the off-link prefix that is also configured for advertisement on the VLAN.

12 No change for the on-link prefix specifically configured by a prefix command, and the off-link prefix that is also configured for advertisement on the VLAN.