IPv6 DHCP Server (DHCPv6) in RouterOS: Configuration Guide

Overview

The DHCPv6 server in MikroTik RouterOS enables automatic IPv6 resource distribution to clients. It supports two primary modes:

Prefix Delegation (DHCPv6-PD): Delegates IPv6 prefixes to downstream routers, which then distribute addresses to their networks via SLAAC or their own DHCPv6 server
Stateful Address Assignment: Assigns individual IPv6 addresses (/128) directly to clients

DHCPv6 is commonly used by ISPs to delegate prefixes to customer routers, or in enterprise environments where centralized address management is required.

Key concept: DHCPv6 does NOT provide default gateway information. Clients receive their default gateway through Router Advertisements (RA), which must be configured separately using Neighbor Discovery (/ipv6 nd).

Prerequisites

Before configuring the DHCPv6 server:

Enable the IPv6 package:

/system package enable ipv6
/system reboot

Verify package is active:
```
/system package print where name=ipv6
```
Have an IPv6 address block to distribute:
- Your own IPv6 allocation (from RIR or ISP)
- A prefix delegated from your upstream provider

How DHCPv6 Server Works

┌─────────────────────────────────────────────────────────────────────┐
│                     Your MikroTik Router                             │
│                                                                      │
│   IPv6 Pool ──────────────────▶ DHCPv6 Server ◀──── ND/RADVD        │
│   (2001:db8::/48)              (Prefix/Address)    (Gateway via RA)  │
└─────────────────────────────────────────────────────────────────────┘
              │                            │
              │ Prefix: 2001:db8:1::/60    │ Gateway: fe80::1
              ▼                            ▼
┌─────────────────────────────────────────────────────────────────────┐
│                     Downstream Router (Client)                       │
│                                                                      │
│   DHCPv6 Client ──▶ IPv6 Pool ──▶ LAN Addresses (SLAAC)             │
│   (Receives /60)    (From /60)    (Assigns /64s to clients)         │
└─────────────────────────────────────────────────────────────────────┘

Menu	Purpose
`/ipv6 dhcp-server`	DHCPv6 server configuration
`/ipv6 dhcp-server binding`	View/manage client bindings
`/ipv6 pool`	IPv6 address pools for delegation
`/ipv6 nd`	Neighbor Discovery (Router Advertisements)

Configuration Properties

DHCPv6 Server Properties

Property	Type	Default	Description
`name`	string	-	Server identifier (required)
`interface`	string	-	Interface to serve DHCPv6 (required)
`address-pool`	string	-	Pool for address assignment (/128 prefixes)
`prefix-pool`	string	-	Pool for prefix delegation
`lease-time`	time	3d	How long clients can use assigned resources
`preference`	integer:0-255	-	Server priority (higher = preferred)
`rapid-commit`	yes/no	yes	Enable two-message exchange (faster)
`route-distance`	integer	-	Distance for routes to DHCPv6 clients
`use-radius`	no/yes/accounting	no	RADIUS integration for authentication/accounting
`disabled`	yes/no	no	Enable/disable server

IPv6 Pool Properties

Property	Type	Default	Description
`name`	string	-	Pool identifier (required)
`prefix`	IPv6 prefix	-	Parent prefix to allocate from
`prefix-length`	integer:1-128	-	Size of delegated prefixes (e.g., 64 for /64s)

Binding Properties

Property	Type	Description
`address`	IPv6 prefix	Assigned prefix or address
`duid`	hex string	Client’s unique identifier
`iaid`	integer	Identity Association Identifier
`server`	string	DHCPv6 server name
`status`	enum	waiting, offered, or bound
`rate-limit`	rx/tx	Bandwidth limit for this binding

Configuration Examples

Example 1: Prefix Delegation for Downstream Routers

Delegate /60 prefixes from a /48 block to customer routers:

# Step 1: Create IPv6 pool for prefix delegation
/ipv6 pool add name=customer-pool prefix=2001:db8::/48 prefix-length=60

# Step 2: Create DHCPv6 server for prefix delegation
/ipv6 dhcp-server add name=dhcpv6-pd interface=ether2-customers \
    prefix-pool=customer-pool lease-time=1d

# Step 3: Verify server is running
/ipv6 dhcp-server print

Expected output:

 # NAME       INTERFACE          ADDRESS-POOL  PREFIX-POOL    LEASE-TIME
 0 dhcpv6-pd  ether2-customers                 customer-pool  1d

Note: The server automatically installs routes to assigned prefixes in the routing table.

Example 2: Stateful Address Assignment

Assign individual IPv6 addresses to clients (useful when SLAAC is not desired):

# Step 1: Create pool with /128 prefix-length for addresses
/ipv6 pool add name=address-pool prefix=2001:db8:100::/64 prefix-length=128

# Step 2: Create DHCPv6 server for address assignment
/ipv6 dhcp-server add name=dhcpv6-addr interface=bridge-lan \
    address-pool=address-pool lease-time=12h

# Step 3: Configure ND to tell clients to use DHCPv6 for addresses
/ipv6 nd set [find interface=bridge-lan] managed-address-configuration=yes

# Step 4: Optionally disable SLAAC (autonomous addressing)
/ipv6 nd prefix set [find interface=bridge-lan] autonomous=no

Example 3: Combined Address and Prefix Delegation

Provide both addresses and prefixes to clients:

# Step 1: Create pools
/ipv6 pool add name=addr-pool prefix=2001:db8:1::/64 prefix-length=128
/ipv6 pool add name=prefix-pool prefix=2001:db8:2::/48 prefix-length=60

# Step 2: Create DHCPv6 server with both pools
/ipv6 dhcp-server add name=dhcpv6-full interface=ether2 \
    address-pool=addr-pool prefix-pool=prefix-pool lease-time=1d

Example 4: DHCPv6 Server on PPPoE

Delegate prefixes to PPPoE clients using PPP profiles:

# Step 1: Create IPv6 pool
/ipv6 pool add name=pppoe-pd-pool prefix=2001:db8::/48 prefix-length=60

# Step 2: Create PPP profile with DHCPv6-PD enabled
/ppp profile add name=pppoe-ipv6 local-address=pool-pppoe \
    dhcpv6-pd-pool=pppoe-pd-pool

# Step 3: Create PPPoE server using the profile
/interface pppoe-server server add interface=ether1 \
    default-profile=pppoe-ipv6 service-name=pppoe-service

Note: PPP automatically creates a dynamic DHCPv6-PD server when clients connect.

Example 5: Static Binding for Specific Client

Reserve a specific prefix for a known client:

# Step 1: Find client's DUID from current bindings
/ipv6 dhcp-server binding print detail

# Step 2: Convert dynamic binding to static
/ipv6 dhcp-server binding make-static [find duid=0x00010001...]

# Step 3: Or create static binding manually
/ipv6 dhcp-server binding add server=dhcpv6-pd \
    duid=0x00010001abcd1234 address=2001:db8:1::/60

Example 6: Rate Limiting DHCPv6 Clients

Limit bandwidth per client binding:

# Step 1: Convert binding to static
/ipv6 dhcp-server binding make-static [find duid=0x00010001...]

# Step 2: Set rate limit (rx/tx in bits per second)
/ipv6 dhcp-server binding set [find duid=0x00010001...] \
    rate-limit=10M/5M

# Step 3: Enable dual-stack queue (optional, combines IPv4/IPv6)
/ipv6 dhcp-server set [find] allow-dual-stack-queue=yes

Example 7: Binding Script for Automation

Execute a script when bindings change:

/ipv6 dhcp-server add name=dhcpv6-pd interface=ether2 \
    prefix-pool=customer-pool script={
        :if ($bindingBound = 1) do={
            :log info "DHCPv6: Prefix $bindingPrefix bound to $bindingDUID"
        } else={
            :log warning "DHCPv6: Prefix released by $bindingDUID"
        }
    }

Available script variables:

Variable	Description
`bindingBound`	1 = bound, 0 = unbound
`bindingServerName`	DHCPv6 server name
`bindingDUID`	Client’s DUID
`bindingAddress`	Assigned address (if applicable)
`bindingPrefix`	Delegated prefix (if applicable)

Understanding Prefix Length in Pools

The prefix-length property determines what size prefixes are delegated:

Pool Prefix	prefix-length	Result	Available Prefixes
/48	60	Delegates /60s	4,096 clients
/48	56	Delegates /56s	256 clients
/48	52	Delegates /52s	16 clients
/56	60	Delegates /60s	16 clients
/56	64	Delegates /64s	256 clients
/64	128	Assigns addresses	18 quintillion addresses

Example: ISP with /32 allocating /56 per customer:

/ipv6 pool add name=isp-pool prefix=2001:db8::/32 prefix-length=56
# Result: 16 million /56 prefixes available

Common Problems and Solutions

Problem 1: Clients Not Receiving Prefixes

Symptom: DHCPv6 server is running but clients stay in “searching” state.

Causes:

Firewall blocking UDP port 547 (server) or 546 (client)
Wrong interface specified
Pool exhausted

Solutions:

# Add firewall rule for DHCPv6 server
/ipv6 firewall filter add chain=input dst-port=547 protocol=udp \
    action=accept comment="Allow DHCPv6 server"

# Verify interface is correct
/ipv6 dhcp-server print

# Check pool usage
/ipv6 pool used print

Problem 2: Routes Not Installed for Delegated Prefixes

Symptom: Server delegates prefix but traffic doesn’t route to client.

Cause: Route installation disabled or distance too high.

Solution:

# Check if routes are being installed
/ipv6 route print where dynamic

# Set appropriate route distance
/ipv6 dhcp-server set [find] route-distance=1

Problem 3: Clients Cannot Reach Internet

Symptom: Client receives prefix but has no connectivity.

Cause: Client not receiving default gateway (Router Advertisements disabled).

Solution:

# On the DHCPv6 server side - ensure ND is configured
/ipv6 nd print
# Should show interface with RA enabled

# On client side - ensure RA acceptance is enabled
/ipv6 settings set accept-router-advertisements=yes

Problem 4: Binding Shows “waiting” Indefinitely

Symptom: Static binding never transitions to “bound” status.

Causes:

Incorrect DUID format
Client not requesting resources
IAID mismatch

Solution:

# Verify DUID from working dynamic binding first
/ipv6 dhcp-server binding print detail where status=bound

# Match DUID format exactly (include 0x prefix)
/ipv6 dhcp-server binding set [find] duid=0x00010001...

Problem 5: Pool Runs Out of Prefixes

Symptom: “no free prefixes” error, new clients cannot connect.

Solutions:

# Check pool usage
/ipv6 pool used print

# Remove stale bindings
/ipv6 dhcp-server binding remove [find status!=bound]

# Reduce lease time to reclaim prefixes faster
/ipv6 dhcp-server set [find] lease-time=4h

# Or expand pool if possible

DHCPv6 Server vs SLAAC

Aspect	DHCPv6 Server	SLAAC (ND)
Address Source	Central server	Client generates from prefix
Management	Centralized, trackable bindings	Decentralized, harder to track
Prefix Delegation	Supported	Not applicable
Best For	ISPs, large networks	Home/small office
Logging	Full binding history	Limited (neighbor table)
Configuration	More complex	Simple (`advertise=yes`)

Verification Commands

# Check DHCPv6 server status
/ipv6 dhcp-server print

# View all bindings
/ipv6 dhcp-server binding print

# View binding details
/ipv6 dhcp-server binding print detail

# Check pool allocation
/ipv6 pool print
/ipv6 pool used print

# Verify routes to delegated prefixes
/ipv6 route print where dynamic

# Check ND configuration
/ipv6 nd print

# Force client reconfiguration (if supported)
/ipv6 dhcp-server binding send-reconfigure [find]

Firewall Considerations

DHCPv6 uses UDP ports:

546: Client port
547: Server port

# Allow DHCPv6 server traffic
/ipv6 firewall filter add chain=input protocol=udp dst-port=547 \
    action=accept comment="DHCPv6 server" place-before=0

# Allow DHCPv6 client responses (if router is also a client)
/ipv6 firewall filter add chain=input protocol=udp dst-port=546 \
    action=accept comment="DHCPv6 client" place-before=0

Prerequisites

IPv6 Addresses - server interface must have IPv6 address

IPv6 Neighbor Discovery - SLAAC (alternative to DHCPv6)
IPv6 DHCP Client - obtain prefix from ISP
IPv6 Firewall - allow UDP 546/547

IPv4 Equivalent

DHCP Server - IPv4 DHCP configuration
DHCP Relay - IPv4 DHCP relay

RADIUS - authentication and accounting

Summary

The RouterOS DHCPv6 server provides:

Prefix Delegation: Delegate blocks of addresses to downstream routers
Address Assignment: Assign individual addresses to clients
RADIUS Integration: Optional authentication and accounting
Rate Limiting: Per-client bandwidth control

Key points:

Create IPv6 pools first, then reference them in the server configuration
prefix-length in pools determines the size of delegated prefixes
DHCPv6 does NOT provide default gateway - configure ND separately
Use managed-address-configuration=yes in ND to signal clients to use DHCPv6
Static bindings allow reservations for specific clients
Routes to delegated prefixes are installed automatically

IPv6 DHCP Server (DHCPv6) in RouterOS: Configuration Guide

IPv6 DHCP Server (DHCPv6) in RouterOS: Configuration Guide

Overview

Prerequisites

How DHCPv6 Server Works

Menu Reference

Configuration Properties

DHCPv6 Server Properties

IPv6 Pool Properties

Binding Properties

Configuration Examples

Example 1: Prefix Delegation for Downstream Routers

Example 2: Stateful Address Assignment

Example 3: Combined Address and Prefix Delegation

Example 4: DHCPv6 Server on PPPoE

Example 5: Static Binding for Specific Client

Example 6: Rate Limiting DHCPv6 Clients

Example 7: Binding Script for Automation

Understanding Prefix Length in Pools

Common Problems and Solutions

Problem 1: Clients Not Receiving Prefixes

Problem 2: Routes Not Installed for Delegated Prefixes

Problem 3: Clients Cannot Reach Internet

Problem 4: Binding Shows “waiting” Indefinitely

Problem 5: Pool Runs Out of Prefixes

DHCPv6 Server vs SLAAC

Verification Commands

Firewall Considerations

Related Topics

Prerequisites

Related IPv6 Services

IPv4 Equivalent

Related Topics

Summary