Stateless Automatic Configuration (SLAAC – Stateless Address Autoconfiguration) in MikroTik

It is a method of address assignment in which devices generate their own unique IPv6 addresses without the need for a DHCP (Dynamic Host Configuration Protocol) server. This form of addressing delivery should be used when we need to deliver automatic IPv6 addressing to end devices.

Next, let's see how SLAAC works:

1. Router Advertisement

In an IPv6 network that uses SLAAC, routers periodically send Router Advertisement (RA) messages to all connected devices on the local network. These messages are multicast (sent to a special address that reaches all devices on the network) and contain important information for autoconfiguration.

2. Prefix Information

The Router Advertisement message contains information about the network prefix. A prefix is ​​a part of the IPv6 address that is common to all devices on the same local network. For example, a typical prefix might be something like “2001:0db8:1abc:”. The length of the prefix can vary and is usually represented as a subnet length value (for example, /64).

3. Interface Identifier

To complete the unique IPv6 address, devices need to add an interface identifier to the prefix information. The portion of the address that represents the interface identifier can be generated in several ways, the most common being using the MAC address of the device's network interface.

4. IPv6 address formation

Once the device receives the Router Advertisement message with the prefix information and has generated its interface identifier, it combines both elements to form its unique IPv6 address.

5. Duplicate detection

Before assigning the IPv6 address to an interface, the device performs a duplicate detection procedure. If another interface on the same network is already using the same address, the device will select a new interface identifier and repeat the process.

6. Address renewal and deactivation

Devices continue to listen to Router Advertisement messages to stay up to date on network configuration. If a router stops sending these messages, devices may assume that IPv6 addresses have become obsolete or that the network has changed, which may cause address renewal or invalid addresses to be disabled.

Example

The configuration is the same as assigning an IPv6 address statically, only the option must be left enabled: Be warned. That is, Advertise's option is to enable SLAAC.

/ipv6 address add address=2001:db8:1234::1 interface=ether1