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# Configuring Neighbor Discovery

To configure Neighbor Discovery:

1. Access an IPv6 interface.
   `
   host1(config)#interface fastEthernet 3/0
   host1(config-if)#
   `
2. Configure the current IPv6 interface to send neighbor solicitations and to respond with neighbor advertisements.
   `
   host1(config)#ipv6 nd
   `

   | Note: This command is redundant when configuring Neighbor Discovery over Ethernet, because router advertisements are automatically sent on Ethernet interfaces. However, unless explicitly enabled, IPv6 router advertisements are not sent on other types of interfaces.

3. (Optional) Configure the interface to retry sending neighbor solicitations using a specified interval.
   `
   host1(config-if)#ipv6 nd ns-interval 500
   `
4. (Optional) Configure the interface to assume that a neighbor is reachable for a specified time after a reachable confirmation event.
   `
   host1(config-if)#ipv6 nd reachable-time 30000
   `
5. (Optional) Configure the interface to suppress router advertisements, as well as replies to router solicitations.
   `
   host1(config-if)#ipv6 nd suppress-ra
   `
6. (Optional) Configure the interface to suppresses the source link-layer option in IPv6 router advertisement transmissions. This action forces neighbors to solicit the router link layer explicitly, and may prove necessary when enabling inbound load sharing across multiple link-layer addresses.
   `
   host1(config-if)#ipv6 nd suppress-ra-source-link-layer
   `
7. (Optional) Configure the interface to send router advertisements at a specified interval.
   `
   host1(config-if)#ipv6 nd ra-interval 500
   `
8. (Optional) Configure the router advertisement lifetime in seconds.
   `
   host1(config-if)#ipv6 nd ra-lifetime 900
   `
9. (Optional) Configure the router advertisement to list a specified prefix, for a valid lifetime and preferred lifetime. The following example also advertises the prefix as reachable on link and that the router can use it as part of the stateless address configuration.
   `
   host1(config-if)#ipv6 nd prefix-advertisement 2002:1::/64 60000 45000 onlink autoconfig
   `
10. (Optional) Configure the router advertisement to contain the “managed address configuration” flag.
    `
    host1(config-if)#ipv6 nd managed-config-flag
    `
11. (Optional) Configure the router advertisement to contain the “other stateful configuration” flag.
    `
    host1(config-if)#ipv6 nd other-config-flag
    `
12. (Optional) Enable active solicitations.
    `
    host1(config-if)#ipv6 nd active-solicitations
    `

## Using IPv6 Profiles and RADIUS to Configure Neighbor Discovery Route Advertisements

In addition to the CLI-based configuration of Neighbor Discovery, you can also use IPv6 profiles to configure Neighbor Discovery route advertisements for dynamically configured interfaces. In addition, you can use RADIUS to configure the prefix in Neighbor Discovery route advertisements for dynamically configured interfaces.

When you configure either a profile-based or RADIUS-based Neighbor Discovery router advertisement, the following considerations apply:

- You can advertise one IPv6 prefix per interface.
- The router advertisement must have a prefix length of 64. For the Ipv6-NdRa-Prefix attribute, the prefix length is in the following format, in which 0040 indicates the prefix length of 64.
  `
  0x 0040 xxxx xxxx xxxx xxxx
  `

  | Note: If both an IPv6 profile and RADIUS are configured for Neighbor Discovery router advertisement, the prefix value returned in RADIUS VSA 26-129 takes precedence over the prefix specified in the IPv6 profile configuration.

### IPv6 Profile-Based Configuration

The JUNOSe software enables you to use profiles to dynamically configure IPv6 interfaces. When you create an IPv6 profile, you can also include Neighbor Discovery route advertisement characteristics, which are then configured on the dynamically-created IPv6 interfaces.

You can include the following commands in IPv6 profiles to configure Neighbor Discovery route advertisement characteristics.

Command | Description
--- | ---
ipv6 nd | Enables Neighbor Discovery on an interface
ipv6 nd managed-config-flag | Sets the “ managed address configuration” flag in IPv6 router advertisements
ipv6 nd other-config-flag | Sets the “ other stateful configuration” flag in IPv6 router advertisements
ipv6 nd prefix-advertisement | Specifies which IPv6 prefixes are included in IPv6 router advertisements
ipv6 nd ra-interval | Configures the interval between IPv6 router advertisements
ipv6 nd ra-lifetime | Configures the router advertisement lifetime
ipv6 nd reachable-time | Configures the amount of time the router can reach an IPv6 node after a reachability confirmation event occurs
ipv6 nd suppress-ra | Disables router advertisement transmissions

For additional information about using IPv6 profiles to configure dynamic interfaces, see Creating an IPv6 Profile in Configuring IPv6 and JUNOSe Link Layer Configuration Guide.

### RADIUS-Based Configuration

You can use RADIUS attribute Ipv6-NdRa-Prefix (VSA 26-129) to configure the prefix used in IPv6 Neighbor Discovery route advertisements. RADIUS then includes the VSA in Access-Accept messages. For information about the Ipv6-NdRa-Prefix RADIUS attribute, see Configuring RADIUS Attributes and RADIUS Attribute Descriptions in the JUNOSe Broadband Access Configuration Guide. .

ipv6 nd

- Use to enable the IPv6 Neighbor Discovery process on an interface.

- Example
  `
  host1(config)#interface fastEthernet 3/0
  host1(config-if)#ipv6 nd
  `

- Use the no version of this command to disable the Neighbor Discovery process.
- See ipv6 nd

ipv6 nd active-solicitations

- Use to specify that the router actively solicit neighbors that become stale (inactive). Normally, when a neighbor entry goes from a reachable state to a stale state, the router drops traffic until it resolves this neighbor entry. When enabled, the ipv6 nd active-solicitations command allows the router to use the stale neighbor entry while it solicits the neighbor. If the neighbor solicitation fails, the router removes the entry from the neighbor table and does not use the neighbor to forward any traffic.

- Example
  `
  host1(config-if)#ipv6 nd active-solicitations
  `

- Use the no version of this command to disable active solicitations.
- See ipv6 nd active-solicitations

ipv6 nd managed-config-flag

- Use to set the “managed address configuration” flag in IPv6 router advertisements.

- Example
  `
  host1(config-if)#ipv6 nd managed-config-flag
  `

- Use the no version of this command to clear the flag from IPv6 router advertisements.
- See ipv6 nd managed-config-flag

ipv6 nd ns-interval

- Use to specify the interval, in milliseconds, between IPv6 neighbor solicitation retransmissions on an interface.

- Example
  `
  host1(config-if)#ipv6 nd ns-interval 500
  `

- Use the no version of this command to return the interval between neighbor solicitation retransmission to its default value (zero [0] milliseconds for router advertisements and 1000 milliseconds for Neighbor Discovery activity of the E-series router).
- See ipv6 nd ns-interval.

ipv6 nd other-config-flag

- Use to set the “other stateful configuration” flag in IPv6 router advertisements.

- Example
  `
  host1(config-if)#ipv6 nd other-config-flag
  `

- Use the no version of this command to clear the flag from IPv6 router advertisements.
- See ipv6 nd other-config-flag

ipv6 nd prefix-advertisement

- Use to specify which IPv6 prefixes the system includes in IPv6 router advertisements.

- Example
  `
  host1(config-if)#ipv6 nd prefix-advertisement 2002:1::/64 60000 45000 onlink autoconfig
  `

- Use the no version of this command to remove any prefixes from the IPv6 routing advertisements.
- See ipv6 nd prefix-advertisement

ipv6 nd ra-interval

- Use to specify the interval, in seconds, between IPv6 router advertisement retransmissions on an interface.

- Example
  `
  host1(config-if)#ipv6 nd ra-interval 500
  `

- Use the no version of this command to restore the default interval,
  200 seconds.
- See ipv6 nd ra-interval

ipv6 nd ra-lifetime

- Use to specify the router lifetime value, in seconds, in IPv6 router advertisements on an interface. The router lifetime value is the amount of time the router is considered the default router on this interface.

- Example
  `
  host1(config-if)#ipv6 nd ra-lifetime 900
  `

- Use the no version of this command to restore the default lifetime,
  1800 seconds.
- See ipv6 nd ra-lifetime

ipv6 nd reachable-time

- Use to specify the amount of time that the E-series router can reach a remote IPv6 node after some reachability confirmation event has occurred.

- Example 1—Sets the reachable-time to 30,000 milliseconds
  `
  host1(config-if)#ipv6 nd reachable-time 30000
  `

- Example 2—Sets the reachable-time to 1 hour, 10 minutes, and 45 seconds
  `
  host1(config-if)#ipv6 nd reachable-time 1 10 45
  `

- Use the no version of this command to restore the default value (zero [0] milliseconds for router advertisements and 3,600,000 milliseconds [1 hour] for Neighbor Discovery activity of the E-series router).
- See ipv6 nd reachable-time

ipv6 nd suppress-ra

- Use to suppress IPv6 router advertisement transmissions on a local area network (Ethernet) interface.

- Example
  `
  host1(config-if)#ipv6 nd suppress-ra
  `

- Use the no version of this command to reenable the sending of IPv6 router advertisement transmissions on the LAN (Ethernet) interface
- See ipv6 nd suppress-ra

ipv6 nd suppress-ra-source-link-layer

- Use to suppress IPv6 router advertisement transmissions on a local area network (Ethernet) interface.

- Example
  `
  host1(config-if)#ipv6 nd suppress-ra-source-link-layer
  `

- Use the no version of this command to reenable the sending of IPv6 router advertisement transmissions on the LAN (Ethernet) interface.
- See ipv6 nd suppress-ra-source-link-layer

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