DHCP Client

Summary

/ip dhcp-client

The DHCP (Dynamic Host Configuration Protocol) is used for the easy distribution of IP addresses in a network. The MikroTik RouterOS implementation includes both server and client parts and is compliant with RFC 2131.

The MikroTik RouterOS DHCP client may be enabled on any Ethernet-like interface at a time. The client will accept an address, netmask, default gateway, and two DNS server addresses. The received IP address will be added to the interface with the respective netmask. The default gateway will be added to the routing table as a dynamic entry. Should the DHCP client be disabled or not renew an address, the dynamic default route will be removed. If there is already a default route installed prior to the DHCP client obtaining one, the route obtained by the DHCP client would be shown as invalid.

RouterOS DHCP client asks for the following options:

• option 1 - SUBNET_MASK,
• option 3 - GATEWAY_LIST,
• option 6 - TAG_DNS_LIST,
• option 33 - STATIC_ROUTE,
• option 42 - NTP_LIST,
• option 121 - CLASSLESS_ROUTE,

DHCP Options

DHCP client has the possibility to set up options that are sent to the DHCP server. For example, hostname and MAC address. The syntax is the same as for DHCP server options.

Currently, there are three variables that can be used in options:

• HOSTNAME;
• CLIENT_MAC - client interface MAC address;
• CLIENT_DUID - client DIUD of the router, same as used for the DHCPv6 client. In conformance with RFC4361

DHCP client default options include these default Options:

Properties

Read-only properties

Menu specific commands

Configuration Examples

Simple DHCP client

Add a DHCP client on the ether1 interface:

/ip dhcp-client add interface=ether1 disabled=no

After the interface is added, you can use the "print" or "print detail" command to see what parameters the DHCP client acquired:

[admin@MikroTik] ip dhcp-client> print detail
Flags: X - disabled, I - invalid 
 0   interface=ether1 add-default-route=yes use-peer-dns=yes use-peer-ntp=yes
     status=bound address=192.168.0.65/24 gateway=192.168.0.1
     dhcp-server=192.168.0.1 primary-dns=192.168.0.1 primary-ntp=192.168.0.1
     expires-after=9m44s 
[admin@MikroTik] ip dhcp-client>

DHCP client status can be checked with:

/ip dhcp-client print detail 

Lease script example

It is possible to execute a script when a DHCP client obtains a new lease or loses an existing one. This is an example script that automatically adds a default route with routing-table=WAN1 and removes it when the lease expires or is removed.

/ip dhcp-client
add add-default-route=no dhcp-options=hostname,clientid disabled=no interface=ether2 script="{\r\
    \n    :local rmark \"WAN1\"\r\
    \n    :local count [/ip route print count-only where comment=\"WAN1\"]\r\
    \n    :if (\$bound=1) do={\r\
    \n        :if (\$count = 0) do={\r\
    \n            /ip route add gateway=\$\"gateway-address\" comment=\"WAN1\" routing-table=\$rmark\r\
    \n        } else={\r\
    \n            :if (\$count = 1) do={\r\
    \n                :local test [/ip route find where comment=\"WAN1\"]\r\
    \n                :if ([/ip route get \$test gateway] != \$\"gateway-address\") do={\r\
    \n                    /ip route set \$test gateway=\$\"gateway-address\"\r\
    \n                }\r\
    \n            } else={\r\
    \n                :error \"Multiple routes found\"\r\
    \n            }\r\
    \n        }\r\
    \n    } else={\r\
    \n        /ip route remove [find comment=\"WAN1\"]\r\
    \n    }\r\
    \n}\r\
    \n"

Resolve default gateway when 'router' (option3) is from a different subnet

In some cases, administrators tend to set the 'router' option which cannot be resolved with offered IP's subnet. For example, the DHCP server offers 192.168.88.100/24 to the client, and option 3 is set to 172.16.1.1. This will result in an unresolved default route:

 #      DST-ADDRESS        PREF-SRC        GATEWAY            DISTANCE
 0  DS  0.0.0.0/0                          172.16.1.1              1
 1 ADC  192.168.88.0/24    192.168.88.100  ether1 

To fix this we need to add /32 route to resolve the gateway over ether1, which can be done by the running script below each time the DHCP client gets an address

/system script add name="dhcpL" source={ /ip address add address=($"lease-address" . "/32") network=$"gateway-address" interface=$interface }

Now we can further extend the script, to check if the address already exists, and remove the old one if changes are needed

/system script add name="dhcpL" source={ 
  /ip address {
    :local ipId [find where comment="dhcpL address"]
    :if ($ipId != "") do={
      :if (!([get $ipId address] = ($"lease-address" . "/32") && [get $ipId network]=$"gateway-address" )) do={
        remove $ipId;
        add address=($"lease-address" . "/32") network=$"gateway-address" \
          interface=$interface comment="dhcpL address"
      }
    } else={
      add address=($"lease-address" . "/32") network=$"gateway-address" \
        interface=$interface comment="dhcpL address"
    }
  }
}

DHCPv6 Client

Summary

Sub-menu: /ipv6 dhcp-client

DHCP-client in RouterOS is capable of being a DHCPv6-client and DHCP-PD client. So it is able to get a prefix from the DHCP-PD server as well as the DHCPv6 stateful address from the DHCPv6 server.

Properties

Read-only properties

Menu specific commands

Script

It is possible to add a script that will be executed when a prefix or an address is acquired and applied or expires and is removed using the DHCP client. There are separated sets of variables that will have the value set by the client depending on prefix or address status change as the client can acquire both and each of them can have a different effect on the router configuration.

Available variables for dhcp-client

• pd-valid - value - 1 or 0 - if prefix is acquired and it is applied or not
• pd-prefix - value ipv6/num (ipv6 prefix with mask) - the prefix inself
• na-valid - value - 1 or 0 - if address is acquired and it is applied or not
• na-address - value - ipv6 address - the address

IAID

To determine what IAID will be used, convert the internal ID of an interface on which the DHCP client is running from hex to decimal.

For example, the DHCP client is running on interface PPPoE-out1. To get internal ID use the following command:

[admin@t36] /interface> :put [find name="pppoe-out1"] 
*15

Now convert hex value 15 to decimal and you get IAID=21

Configuration Examples

Simple DHCPv6 client

This simple example demonstrates how to enable dhcp client to receive IPv6 prefix and add it to the pool.

/ipv6 dhcp-client add request=prefix pool-name=test-ipv6 pool-prefix-length=64 interface=ether13 

Detailed print should show status of the client and we can verify if prefix is received

[admin@x86-test] /ipv6 dhcp-client> print detail 
Flags: D - dynamic, X - disabled, I - invalid
 0 interface=bypass pool-name="test-ipv6" pool-prefix-length=64 status=bound 
prefix=2001:db8:7501:ff04::/62 expires-after=2d23h11m53s request=prefix

Notice that server gave us prefix 2a02:610:7501:ff04::/62 . And it should be also added to ipv6 pools

[admin@MikroTik] /ipv6 pool> print 
Flags: D - dynamic 
# NAME PREFIX REQUEST PREFIX-LENGTH
0 D test-ipv6 2001:db8:7501:ff04::/62 prefix 64

It works! Now you can use this pool, for example, for pppoe clients.

Use received prefix for local RA

Consider following setup:

• ISP is routing prefix 2001:DB8::/62 to the router R1
• Router R1 runs DHCPv6 server to delegate /64 prefixes to the customer routers CE1 CE2
• DHCP client on routers CE1 and CE2 receives delegated /64 prefix from the DHCP server (R1).
• Client routers uses received prefix to set up RA on the local interface

Configuration

R1

/ipv6 route 
add gateway=fe80::1:1%to-ISP 

/ipv6 pool 
add name=myPool prefix=2001:db8::/62 prefix-length=64 

/ipv6 dhcp-server
 add address-pool=myPool disabled=no interface=to-CE-routers lease-time=3m name=server1

CE1

/ipv6 dhcp-client
add interface=to-R1 request=prefix pool-name=my-ipv6

/ipv6 address
add address=::1/64 from-pool=my-ipv6 interface=to-clients advertise=yes

CE2

/ipv6 dhcp-client
 add interface=to-R1 request=prefix pool-name=my-ipv6 
/ipv6 address add address=::1/64 from-pool=my-ipv6 interface=to-clients advertise=yes

Check the status

After configuration is complete we can verify that each CE router received its own prefix

On server:

[admin@R1] /ipv6 dhcp-server binding> print
 Flags: X - disabled, D - dynamic 
# ADDRESS DUID IAID SERVER STATUS
 1 D 2001:db8:1::/64 0019d1393536 566 server1 bound 
2 D 2001:db8:2::/64 0019d1393535 565 server1 bound

On client:

[admin@CE1] /ipv6 dhcp-client> print 
Flags: D - dynamic, X - disabled, I - invalid 
# INTERFACE STATUS REQUEST PREFIX 
0 to-R1 bound prefix 2001:db8:1::/64 

[admin@CE1] /ipv6 dhcp-client> /ipv6 pool print 
Flags: D - dynamic 
# NAME PREFIX PREFIX-LENGTH
0 D my-ipv6 2001:db8:1::/64 64

We can also see that IPv6 address was automatically added from the prefix pool:

[admin@CE1] /ipv6 address> print 
Flags: X - disabled, I - invalid, D - dynamic, G - global, L - link-local 
# ADDRESS FROM-POOL INTERFACE ADVERTISE 0 G 2001:db8:1::1/64 to-clients yes 
..

And pool usage shows that 'Address' is allocating the pool

[admin@CE1] /ipv6 pool used> print
 POOL PREFIX OWNER INFO 
my-ipv6 2001:db8:1::/64 Address to-clients

DHCP Server

Summary

The DHCP (Dynamic Host Configuration Protocol) is used for the easy distribution of IP addresses in a network. The MikroTik RouterOS implementation includes both server and client parts and is compliant with RFC 2131.

The router supports an individual server for each Ethernet-like interface. The MikroTik RouterOS DHCP server supports the basic functions of giving each requesting client an IP address/netmask lease, default gateway, domain name, DNS-server(s) and WINS-server(s) (for Windows clients) information (set up in the DHCP networks submenu)

In order for the DHCP server to work, IP pools must also be configured (do not include the DHCP server's own IP address into the pool range) and the DHCP networks.

It is also possible to hand out leases for DHCP clients using the RADIUS server; the supported parameters for a RADIUS server are as follows:

Access-Request:

• NAS-Identifier - router identity
• NAS-IP-Address - IP address of the router itself
• NAS-Port - unique session ID
• NAS-Port-Type - Ethernet
• Calling-Station-Id - client identifier (active-client-id)
• Framed-IP-Address - IP address of the client (active-address)
• Called-Station-Id - the name of DHCP server
• User-Name - MAC address of the client (active-mac-address)
• Password - " "

Access-Accept:

• Framed-IP-Address - IP address that will be assigned to a client
• Framed-Pool - IP pool from which to assign an IP address to a client
• Rate-Limit - Datarate limitation for DHCP clients. Format is: rx-rate[/tx-rate] [rx-burst-rate[/tx-burst-rate] [rx-burst-threshold[/tx-burst-threshold] [rx-burst-time[/tx-burst-time][priority] [rx-rate-min[/tx-rate-min]]]]. All rates should be numbers with optional 'k' (1,000s) or 'M' (1,000,000s). If tx-rate is not specified, rx-rate is as tx-rate too. Same goes for tx-burst-rate and tx-burst-threshold and tx-burst-time. If both rx-burst-threshold and tx-burst-threshold are not specified (but burst-rate is specified), rx-rate and tx-rate are used as burst thresholds. If both rx-burst-time and tx-burst-time are not specified, 1s is used as default. Priority takes values 1..8, where 1 implies the highest priority, but 8 - the lowest. If rx-rate-min and tx-rate-min are not specified rx-rate and tx-rate values are used. The rx-rate-min and tx-rate-min values can not exceed rx-rate and tx-rate values.
• Ascend-Data-Rate - TX/RX data rate limitation if multiple attributes are provided, first limits tx data rate, second - RX data rate. If used together with Ascend-Xmit-Rate, specifies RX rate. 0 if unlimited
• Ascend-Xmit-Rate - tx data rate limitation. It may be used to specify the TX limit only instead of sending two sequential Ascend-Data-Rate attributes (in that case Ascend-Data-Rate will specify the receive rate). 0 if unlimited
• Session-Timeout - max lease time (lease-time)

DHCP Server Properties

Leases

Sub-menu: /ip dhcp-server lease

DHCP server lease submenu is used to monitor and manage server leases. The issued leases are shown here as dynamic entries. You can also add static leases to issue a specific IP address to a particular client (identified by MAC address).

Generally, the DHCP lease is allocated as follows:

• an unused lease is in the "waiting" state
• if a client asks for an IP address, the server chooses one
• if the client receives a statically assigned address, the lease becomes offered, and then bound with the respective lease time
• if the client receives a dynamic address (taken from an IP address pool), the router sends a ping packet and waits for an answer for 0.5 seconds. During this time, the lease is marked testing
• in the case where the address does not respond, the lease becomes offered and then bound with the respective lease time
• in other cases, the lease becomes busy for the lease time (there is a command to retest all busy addresses), and the client's request remains unanswered (the client will try again shortly)

A client may free the leased address. The dynamic lease is removed, and the allocated address is returned to the address pool. But the static lease becomes busy until the client reacquires the address.

Menu specific commands

Store Configuration

Sub-menu: /ip dhcp-server config

Store Leases On Disk: The configuration of how often the DHCP leases will be stored on disk. If they would be saved on a disk on every lease change, a lot of disk writes would happen which is very bad for Compact Flash (especially, if lease times are very short). To minimize writes on disk, all changes are saved on disk every store-leases-disk seconds. Additionally, leases are always stored on disk on graceful shutdown and reboot.

Manual changes to leases - addition/removal of a static lease, removal of a dynamic lease will cause changes to be pushed for this lease to storage.

Accounting: The accounting parameter in the DHCP server configuration enables or disables accounting for DHCP leases. When accounting is enabled, the DHCP server logs information about IP address assignments and lease renewals. This information can be useful for tracking and monitoring network usage, analyzing traffic patterns, or generating reports on IP address allocations.

Interim-update: The interim-update parameter determines whether the DHCP server sends periodic updates to the accounting server during a lease. These updates provide information about the lease duration, usage, and other relevant details. Enabling interim updates allows for more accurate tracking of lease activity.

Radius-password: The radius-password parameter is used to set the password for the RADIUS (Remote Authentication Dial-In User Service) server. RADIUS is a networking protocol commonly used for providing centralized authentication, authorization, and accounting for network access. When configuring the DHCP server to communicate with a RADIUS server for authentication or accounting purposes, you need to specify the correct password to establish a secure connection. This parameter ensures that the DHCP server can authenticate with the RADIUS server using the specified password.

Rate limiting

It is possible to set the bandwidth to a specific IPv4 address by using DHCPv4 leases. This can be done by setting a rate limit on the DHCPv4 lease itself, by doing this a dynamic simple queue rule will be added for the IPv4 address that corresponds to the DHCPv4 lease. By using the rate-limit parameter you can conveniently limit a user's bandwidth.

First, make the DHCPv4 lease static, otherwise, it will not be possible to set a rate limit to a DHCPv4 lease:

[admin@MikroTik] > /ip dhcp-server lease print 
Flags: X - disabled, R - radius, D - dynamic, B - blocked 
 #   ADDRESS               MAC-ADDRESS       HOST-NAME               SERVER               RATE-LIMIT               STATUS 
 0 D 192.168.88.254        6C:3B:6B:7C:41:3E MikroTik                DHCPv4_Server                                 bound 

[admin@MikroTik] > /ip dhcp-server lease make-static 0

[admin@MikroTik] > /ip dhcp-server lease print 
Flags: X - disabled, R - radius, D - dynamic, B - blocked 
 #   ADDRESS               MAC-ADDRESS       HOST-NAME               SERVER               RATE-LIMIT               STATUS 
 0   192.168.88.254        6C:3B:6B:7C:41:3E MikroTik                DHCPv4_Server                                 bound

Then you can set a rate to a DHCPv4 lease that will create a new dynamic simple queue entry:

[admin@MikroTik] > /ip dhcp-server lease set 0 rate-limit=10M/10M

[admin@MikroTik] > /queue simple print 
Flags: X - disabled, I - invalid, D - dynamic 
 0  D name="dhcp-ds<6C:3B:6B:7C:41:3E>" target=192.168.88.254/32 parent=none packet-marks="" priority=8/8 queue=default-small/default-small limit-at=10M/10M max-limit=10M/10M burst-limit=0/0 burst-threshold=0/0 burst-time=0s/0s 
      bucket-size=0.1/0.1

If allow-dual-stack-queue is enabled, then a single dynamic simple queue entry will be created containing both IPv4 and IPv6 addresses:

[admin@MikroTik] > /queue simple print 
Flags: X - disabled, I - invalid, D - dynamic 
 0  D name="dhcp-ds<6C:3B:6B:7C:41:3E>" target=192.168.88.254/32,fdb4:4de7:a3f8:418c::/66 parent=none packet-marks="" priority=8/8 queue=default-small/default-small limit-at=10M/10M max-limit=10M/10M burst-limit=0/0 burst-threshold=0/0 
      burst-time=0s/0s bucket-size=0.1/0.1 

Network

Sub-menu: /ip dhcp-server network

Properties

RADIUS Support

Since RouterOS v6.43 it is possible to use RADIUS to assign a rate limit per lease, to do so you need to pass the Mikrotik-Rate-Limit attribute from your RADIUS Server for your lease. To achieve this you first need to set your DHCPv4 Server to use RADIUS for assigning leases. Below is an example of how to set it up:

/radius
add address=10.0.0.1 secret=VERYsecret123 service=dhcp
/ip dhcp-server
set dhcp1 use-radius=yes

After that, you need to tell your RADIUS Server to pass the Mikrotik-Rate-Limit attribute. In case you are using FreeRADIUS with MySQL, then you need to add appropriate entries into radcheck and radreply tables for a MAC address, that is being used for your DHCPv4 Client. Below is an example for table entries:

INSERT INTO `radcheck` (`username`, `attribute`, `op`, `value`) VALUES
('00:0C:42:00:D4:64', 'Auth-Type', ':=', 'Accept'),

INSERT INTO `radreply` (`username`, `attribute`, `op`, `value`) VALUES
('00:0C:42:00:D4:64', 'Framed-IP-Address', '=', '192.168.88.254'),
('00:0C:42:00:D4:64', 'Mikrotik-Rate-Limit', '=', '10M'),

Alerts

To find any rogue DHCP servers as soon as they appear in your network, the DHCP Alert tool can be used. It will monitor the interface for all DHCP replies and check if this reply comes from a valid DHCP server. If a reply from an unknown DHCP server is detected, an alert gets triggered:

[admin@MikroTik] ip dhcp-server alert>/log print
00:34:23 dhcp,critical,error,warning,info,debug dhcp alert on Public:
    discovered unknown dhcp server, mac 00:02:29:60:36:E7, ip 10.5.8.236
[admin@MikroTik] ip dhcp-server alert>

When the system alerts about a rogue DHCP server, it can execute a custom script.

As DHCP replies can be unicast, the rogue DHCP detector may not receive any offer to other DHCP clients at all. To deal with this, the rogue DHCP detector acts as a DHCP client as well - it sends out DHCP discover requests once a minute.

Sub-menu: /ip dhcp-server alert

Properties

Read-only properties

Menu specific commands

DHCP Options

Sub-menu: /ip dhcp-server option

With the help of the DHCP Option list, it is possible to define additional custom options for DHCP Server to advertise. Option precedence is as follows:

• radius,
• lease,
• server,
• network.

This is the order in which the client option request will be filled in.

According to the DHCP protocol, a parameter is returned to the DHCP client only if it requests this parameter, specifying the respective code in the DHCP request Parameter-List (code 55) attribute. If the code is not included in the Parameter-List attribute, the DHCP server will not send it to the DHCP client, but since RouterOS v7.1rc5 it is possible to force the DHCP option from the server-side even if the DHCP-client does not request such parameter:

ip/dhcp-server/option/set force=yes

Properties

DHCP Option Sets

Sub-menu: /ip dhcp-server option sets

This menu allows combining multiple options in option sets, which later can be used to override the default DHCP server option set.

Example

Classless Route

A classless route adds a specified route in the clients routing table. In our example, it will add

• dst-address=160.0.0.0/24 gateway=10.1.101.1
• dst-address=0.0.0.0/0 gateway=10.1.101.1

According to RFC 3442: The first part is the netmask ("18" = netmask /24). Second part is significant part of destination network ("A00000" = 160.0.0). Third part is IP address of gateway ("0A016501" = 10.1.101.1). Then There are parts of the default route, destination netmask (0x00 = 0.0.0.0/0) followed by default route (0x0A016501 = 10.1.101.1)

/ip dhcp-server option
add code=121 name=classless value=0x18A000000A016501000A016501
/ip dhcp-server network
set 0 dhcp-option=classless

Result:

[admin@MikroTik] /ip route> print
Flags: X - disabled, A - active, D - dynamic, C - connect, S - static, r - rip, b - bgp, o - ospf,
m - mme, B - blackhole, U - unreachable, P - prohibit
 #      DST-ADDRESS        PREF-SRC        GATEWAY            DISTANCE
 0 ADS  0.0.0.0/0                          10.1.101.1         0
 1 ADS  160.0.0.0/24                       10.1.101.1         0

A much more robust way would be to use built-in variables, the previous example can be rewritten as:

/ip dhcp-server option 
add name=classless code=121 value="0x18A00000\$(NETWORK_GATEWAY)0x00\$(NETWORK_GATEWAY)"

Auto proxy config

/ip dhcp-server option 
  add code=252 name=auto-proxy-config value="'https://autoconfig.something.lv/wpad.dat'"

Vendor Classes

Since the 6.45beta6 version RouterOS support vendor class, ID matcher. The vendor class is used by DHCP clients to optionally identify the vendor and configuration.

Example

In the following configuration example, we will give an IP address from a particular pool for an Android-based mobile phone. We will use the RouterBOARD with a default configuration

/ip pool
add name=default-dhcp ranges=192.168.88.10-192.168.88.254
add name=pool-for-VID ranges=172.16.16.10-172.16.16.120

Configure vendor-class-id matcher. DHCP servers configuration remains the default

/ip dhcp-server
add address-pool=default-dhcp disabled=no interface=bridge name=defconf
/ip dhcp-server network
add address=192.168.88.0/24 comment=defconf gateway=192.168.88.1
/ip dhcp-server vendor-class-id
add address-pool=pool-for-VID name=samsung server=defconf vid=android-dhcp-9

Connect your mobile phone to the device to receive an IP address from the 172.16.16.0 network

[admin@mikrotik] > /ip dhcp-server lease print detail 
Flags: X - disabled, R - radius, D - dynamic, B - blocked 
 0 D address=172.16.16.120 mac-address=30:07:4D:F5:07:49 client-id="1:30:7:4d:f5:7:49" address-lists="" server=defconf dhcp-option="" 
     status=bound expires-after=8m55s last-seen=1m5s active-address=172.16.16.120 active-mac-address=30:07:4D:F5:07:49 
     active-client-id="1:30:7:4d:f5:7:49" active-server=defconf host-name="Galaxy-S8"

If you do not know your devices Vendor Class ID, you can turn on DHCP debug logs with /system logging add topics=dhcp. Then in the logging entries, you will see Class-ID

10:30:31 dhcp,debug,packet defconf received request with id 4238230732 from 0.0.0.0 
10:30:31 dhcp,debug,packet     secs = 3 
10:30:31 dhcp,debug,packet     ciaddr = 0.0.0.0 
10:30:31 dhcp,debug,packet     chaddr = 30:07:4D:F5:07:49 
10:30:31 dhcp,debug,packet     Msg-Type = request 
10:30:31 dhcp,debug,packet     Client-Id = 01-30-07-4D-F5-07-49 
10:30:31 dhcp,debug,packet     Address-Request = 172.16.16.120 
10:30:31 dhcp,debug,packet     Server-Id = 192.168.88.1 
10:30:31 dhcp,debug,packet     Max-DHCP-Message-Size = 1500 
10:30:31 dhcp,debug,packet     Class-Id = "android-dhcp-9" 
10:30:31 dhcp,debug,packet     Host-Name = "Galaxy-S8" 
10:30:31 dhcp,debug,packet     Parameter-List = Subnet-Mask,Router,Domain-Server,Domain-Name,Interface-MTU,Broadcast-Address,Address-Time,Ren
ewal-Time,Rebinding-Time,Vendor-Specific 
10:30:31 dhcp,info defconf assigned 172.16.16.120 to 30:07:4D:F5:07:49 
10:30:31 dhcp,debug,packet defconf sending ack with id 4238230732 to 172.16.16.120 
10:30:31 dhcp,debug,packet     ciaddr = 0.0.0.0 
10:30:31 dhcp,debug,packet     yiaddr = 172.16.16.120 
10:30:31 dhcp,debug,packet     siaddr = 192.168.88.1 
10:30:31 dhcp,debug,packet     chaddr = 30:07:4D:F5:07:49 
10:30:31 dhcp,debug,packet     Msg-Type = ack 
10:30:31 dhcp,debug,packet     Server-Id = 192.168.88.1 
10:30:31 dhcp,debug,packet     Address-Time = 600 
10:30:31 dhcp,debug,packet     Domain-Server = 192.168.88.1,10.155.0.1,10.155.0.126 

Generic matcher

Since RouterOS 7.4beta4 (2022-Jun-15 14:04) the vendor-id matcher is converted to a generic matcher. The genric matcher allows matching any of the DHCP options.

And an example to match DHCP option 60 similar to vendor-id-class matcher:

/ip dhcp-server matcher
add address-pool=pool1 code=60 name=test value=android-dhcp-11

Match the client-id with option 61 configured as hex value:

/ip dhcp-server matcher
add address-pool=pool1 code=61 name=test value=0x016c3b6bed8364

Match the code 12 using the string:

/ip dhcp-server matcher
add address-pool=testpool code=12 name=test server=dhcp1 value="MikroTik"

Configuration Examples

Setup

To simply configure DHCP server you can use a setup command.

First, you configure an IP address on the interface:

[admin@MikroTik] > /ip address add address=192.168.88.1/24 interface=ether3 disabled=no

Then you use setup a command which will automatically ask necessary parameters:

[admin@MikroTik] > /ip dhcp-server setup 
Select interface to run DHCP server on 

dhcp server interface: ether3
Select network for DHCP addresses 

dhcp address space: 192.168.88.0/24
Select gateway for given network 

gateway for dhcp network: 192.168.88.1
Select pool of ip addresses given out by DHCP server 

addresses to give out: 192.168.88.2-192.168.88.254
Select DNS servers 

dns servers: 10.155.126.1,10.155.0.1,                               
Select lease time 

lease time: 10m

That is all. You have configured an active DHCP server.

Manual configuration

To configure the DHCP server manually to respond to local requests you have to configure the following:

• An IP pool for addresses to be given out, make sure that your gateway/DHCP server address is not part of the pool.

/ip pool add name=dhcp_pool0 ranges=192.168.88.2-192.168.88.254

• A network indicating subnets that DHCP-server will lease addresses from, among other information, like a gateway, DNS-server, NTP-server, DHCP options, etc.

/ip dhcp-server network add address=192.168.88.0/24 dns-server=192.168.88.1 gateway=192.168.88.1

• In our case, the device itself is serving as the gateway, so we'll add the address to the bridge interface:

/ip address add address=192.168.88.1/24 interface=bridge1 network=192.168.88.0

• And finally, add DHCP Server, here we will add the previously created address pool, and specify on which interface the DHCP server should work on

/ip dhcp-server add address-pool=dhcp_pool0 disabled=no interface=bridge1 name=dhcp1

DHCPv6 Server

Summary

Standards: RFC 3315, RFC 3633

Single DUID is used for client and server identification, only IAID will vary between clients corresponding to their assigned interface.

Client binding creates a dynamic pool with a timeout set to binding's expiration time (note that now dynamic pools can have a timeout), which will be updated every time binding gets renewed.

When a client is bound to a prefix, the DHCP server adds routing information to know how to reach the assigned prefix.

Client bindings in the server do not show MAC address anymore (as it was in v5.8), DUID (hex) and IAID are used instead. After upgrade, MAC addresses will be converted to DUIDs automatically, but due to unknown DUID type and unknown IAID, they should be further updated by the user;

General

Sub-menu: /ipv6 dhcp-server

This sub-menu lists and allows to configure DHCP-PD servers.

DHCPv6 Server Properties

Read-only Properties

Bindings

Sub-menu: /ipv6 dhcp-server binding

DUID is used only for dynamic bindings, so if it changes then the client will receive a different prefix than previously.

Read-only properties

For example, dynamically assigned /62 prefix

[admin@RB493G] /ipv6 dhcp-server binding> print detail
 Flags: X - disabled, D - dynamic 
0 D address=2a02:610:7501:ff00::/62 duid="1605fcb400241d1781f7" iaid=0
 server=local-dhcp life-time=3d status=bound expires-after=2d23h40m10s 
last-seen=19m50s 
1 D address=2a02:610:7501:ff04::/62 duid="0019d1393535" iaid=2 
server=local-dhcp life-time=3d status=bound expires-after=2d23h43m47s 
last-seen=16m13s

Menu specific commands

Rate limiting

It is possible to set the bandwidth to a specific IPv6 address by using DHCPv6 bindings. This can be done by setting a rate limit on the DHCPv6 binding itself, by doing this a dynamic simple queue rule will be added for the IPv6 address that corresponds to the DHCPv6 binding. By using the rate-limit the parameter you can conveniently limit a user's bandwidth.

First, make the DHCPv6 binding static, otherwise, it will not be possible to set a rate limit to a DHCPv6 binding:

[admin@MikroTik] > /ipv6 dhcp-server binding print 
Flags: X - disabled, D - dynamic 
# ADDRESS DUID SERVER STATUS 
0 D fdb4:4de7:a3f8:418c::/66 0x6c3b6b7c413e DHCPv6_Server bound

[admin@MikroTik] > /ipv6 dhcp-server binding make-static 0

[admin@MikroTik] > /ipv6 dhcp-server binding print
Flags: X - disabled, D - dynamic 
# ADDRESS DUID SERVER STATUS 
0 fdb4:4de7:a3f8:418c::/66 0x6c3b6b7c413e DHCPv6_Server bound 

Then you need can set a rate to a DHCPv6 binding that will create a new dynamic simple queue entry:

[admin@MikroTik] > /ipv6 dhcp-server binding set 0 rate-limit=10M/10 
[admin@MikroTik] > /queue simple print 
Flags: X - disabled, I - invalid, D - dynamic 
0 D name="dhcp<6c3b6b7c413e fdb4:4de7:a3f8:418c::/66>" target=fdb4:4de7:a3f8:418c::/66 parent=none packet-marks="" priority=8/8 queue=default
-small/default-small limit-at=10M/10M max-limit=10M/10M burst-limit=0/0 
burst-threshold=0/0 burst-time=0s/0s bucket-size=0.1/0.1

If allow-dual-stack-queue is enabled, then a single dynamic simple queue entry will be created containing both IPv4 and IPv6 addresses:

[admin@MikroTik] > /queue simple print 
Flags: X - disabled, I - invalid, D - dynamic
 0 D name="dhcp-ds<6C:3B:6B:7C:41:3E>" target=192.168.1.200/32,fdb4:4de7:a3f8:418c::/66 parent=none packet-marks="" priority=8/8 queue=default
-small/default-small limit-at=10M/10M max-limit=10M/10M 
burst-limit=0/0 burst-threshold=0/0 burst-time=0s/0s bucket-size=0.1/0.1

RADIUS Support

Since RouterOS v6.43 it is possible to use RADIUS to assign a rate-limit per DHCPv6 binding, to do so you need to pass the Mikrotik-Rate-Limit attribute from your RADIUS Server for your DHCPv6 binding. To achieve this you first need to set your DHCPv6 Server to use RADIUS for assigning bindings. Below is an example of how to set it up:

/radius 
add address=10.0.0.1 secret=VERYsecret123 service=dhcp 
/ipv6 dhcp-server 
set dhcp1 use-radius=yes

After that, you need to tell your RADIUS Server to pass the Mikrotik-Rate-Limit attribute. In case you are using FreeRADIUS with MySQL, then you need to add appropriate entries into radcheck and radreply tables for a MAC address, that is being used for your DHCPv6 Client. Below is an example for table entries:

INSERT INTO `radcheck` (`username`, `attribute`, `op`, `value`) VALUES 
('000c4200d464', 'Auth-Type', ':=', 'Accept'),
 INSERT INTO `radreply` (`username`, `attribute`, `op`, `value`) VALUES 
('000c4200d464', 'Delegated-IPv6-Prefix', '=', 'fdb4:4de7:a3f8:418c::/66'), 
('000c4200d464', 'Mikrotik-Rate-Limit', '=', '10M');

Configuration Example

Enabling IPv6 Prefix delegation

Let's consider that we already have a running DHCP server.

To enable IPv6 prefix delegation, first, we need to create an address pool:

/ipv6 pool add name=myPool prefix=2001:db8:7501::/60 prefix-length=62

Notice that prefix-length is 62 bits, which means that clients will receive /62 prefixes from the /60 pool.

The next step is to enable DHCP-PD:

/ipv6 dhcp-server add name=myServer address-pool=myPool interface=local

To test our server we will set up wide-dhcpv6 on an ubuntu machine:

• install wide-dhcpv6-client
• edit "/etc/wide-dhcpv6/dhcp6c.conf" as above

interface eth2{
send ia-pd 0;
};

id-assoc pd {
prefix-interface eth3{
sla-id 1;
sla-len 2;
};
};

• Run DHCP-PD client:

sudo dhcp6c -d -D -f eth2

• Verify that prefix was added to the:

mrz@bumba:/media/aaa$ ip -6 addr
 .. 
2: eth3: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qlen 1000
 inet6 2001:db8:7501:1:200:ff:fe00:0/64 scope global
 valid_lft forever preferred_lft forever
 inet6 fe80::224:1dff:fe17:81f7/64 scope link
 valid_lft forever preferred_lft forever

• You can make binding to specific client static so that it always receives the same prefix:

[admin@RB493G] /ipv6 dhcp-server binding> print 
Flags: X - disabled, D - dynamic 
# ADDRESS DU IAID SER.. STATUS 0 D 2001:db8:7501:1::/62 16 0 loc.. bound 
[admin@RB493G] /ipv6 dhcp-server binding> make-static 0

• DHCP-PD also installs a route to assigned prefix into IPv6 routing table:

[admin@RB493G] /ipv6 route> print
 Flags: X - disabled, A - active, D - dynamic, C - connect, S - static, r - rip, o - ospf, b - bgp, U - unreachable
 # DST-ADDRESS GATEWAY DISTANCE 
... 
2 ADS 2001:db8:7501:1::/62 fe80::224:1dff:fe17:8... 1

DHCP Relay

Summary

Sub-menu: /ip dhcp-relay

The purpose of the DHCP relay is to act as a proxy between DHCP clients and the DHCP server. It is useful in networks where the DHCP server is not on the same broadcast domain as the DHCP client.

DHCP relay does not choose the particular DHCP server in the DHCP-server list, it just sends the incoming request to all the listed servers.

Properties

Configuration Example

Let us consider that you have several IP networks 'behind' other routers, but you want to keep all DHCP servers on a single router. To do this, you need a DHCP relay on your network which will relay DHCP requests from clients to the DHCP server.

This example will show you how to configure a DHCP server and a DHCP relay that serves 2 IP networks - 192.168.1.0/24 and 192.168.2.0/24 that are behind a router DHCP-Relay.

IP Address Configuration

IP addresses of DHCP-Server:

[admin@DHCP-Server] ip address> print
Flags: X - disabled, I - invalid, D - dynamic
 #   ADDRESS            NETWORK         BROADCAST       INTERFACE
 0   192.168.0.1/24     192.168.0.0     192.168.0.255   To-DHCP-Relay
 1   10.1.0.2/24	10.1.0.0	10.1.0.255	Public
[admin@DHCP-Server] ip address>

IP addresses of DHCP-Relay:

[admin@DHCP-Relay] ip address> print
Flags: X - disabled, I - invalid, D - dynamic
 #   ADDRESS            NETWORK         BROADCAST       INTERFACE
 0   192.168.0.2/24     192.168.0.0     192.168.0.255   To-DHCP-Server
 1   192.168.1.1/24     192.168.1.0     192.168.1.255   Local1
 2   192.168.2.1/24     192.168.2.0     192.168.2.255   Local2
[admin@DHCP-Relay] ip address>

DHCP Server Setup

To setup 2 DHCP Servers on the DHCP-Server router add 2 pools. For networks 192.168.1.0/24 and 192.168.2.0:

/ip pool add name=Local1-Pool ranges=192.168.1.11-192.168.1.100
/ip pool add name=Local2-Pool ranges=192.168.2.11-192.168.2.100
[admin@DHCP-Server] ip pool> print
 # NAME                                         RANGES
 0 Local1-Pool                                  192.168.1.11-192.168.1.100
 1 Local2-Pool                                  192.168.2.11-192.168.2.100
[admin@DHCP-Server] ip pool>

Create DHCP Servers:

/ip dhcp-server add interface=To-DHCP-Relay relay=192.168.1.1 \
   address-pool=Local1-Pool name=DHCP-1 disabled=no
/ip dhcp-server add interface=To-DHCP-Relay relay=192.168.2.1 \
   address-pool=Local2-Pool name=DHCP-2 disabled=no
[admin@DHCP-Server] ip dhcp-server> print
Flags: X - disabled, I - invalid
 #   NAME         INTERFACE     RELAY           ADDRESS-POOL LEASE-TIME ADD-ARP
 0   DHCP-1       To-DHCP-Relay 192.168.1.1     Local1-Pool  3d00:00:00
 1   DHCP-2       To-DHCP-Relay 192.168.2.1     Local2-Pool  3d00:00:00
[admin@DHCP-Server] ip dhcp-server>

Configure respective networks:

/ip dhcp-server network add address=192.168.1.0/24 gateway=192.168.1.1 \
   dns-server=159.148.60.20
/ip dhcp-server network add address=192.168.2.0/24 gateway=192.168.2.1 \
   dns-server 159.148.60.20
[admin@DHCP-Server] ip dhcp-server network> print
 # ADDRESS            GATEWAY         DNS-SERVER      WINS-SERVER     DOMAIN
 0 192.168.1.0/24     192.168.1.1     159.148.60.20
 1 192.168.2.0/24     192.168.2.1     159.148.60.20
[admin@DHCP-Server] ip dhcp-server network>

DHCP Relay Config

Configuration of DHCP-Server is done. Now let's configure DHCP-Relay:

/ip dhcp-relay add name=Local1-Relay interface=Local1 \
   dhcp-server=192.168.0.1 local-address=192.168.1.1 disabled=no
/ip dhcp-relay add name=Local2-Relay interface=Local2 \
   dhcp-server=192.168.0.1 local-address=192.168.2.1 disabled=no
[admin@DHCP-Relay] ip dhcp-relay> print
Flags: X - disabled, I - invalid
 #   NAME                        INTERFACE      DHCP-SERVER     LOCAL-ADDRESS
 0   Local1-Relay                Local1         192.168.0.1     192.168.1.1
 1   Local2-Relay                Local2         192.168.0.1     192.168.2.1
[admin@DHCP-Relay] ip dhcp-relay>

DHCP Relay with VRF (introduced in 7.15)

Let's take the previous setup but we'll consider that the interface to the DHCP server and interfaces to DHCP clients are added in VRF:

/ip vrf
add interfaces=To-DHCP-Server name=vrf_server
add interfaces=Local2 name=vrf2
add interfaces=Local1 name=vrf1

In the DHCP-relay configuration dhcp-server-vrf should be added:

/ip dhcp-relay/set dhcp-server-vrf=vrf_server numbers=0,1

Due to VRF configuration there are several routing-tables - we should add additional routes:

/ip route
add disabled=no distance=1 dst-address=192.168.0.0/24 gateway=To-DHCP-Server@vrf_server pref-src="" routing-table=vrf1 scope=10 suppress-hw-offload=no \
    target-scope=10
add disabled=no distance=1 dst-address=192.168.0.0/24 gateway=To-DHCP-Server@vrf_server pref-src="" routing-table=vrf2 scope=10 suppress-hw-offload=no \
    target-scope=10
add disabled=no dst-address=192.168.1.0/24 gateway=Local1@vrf1 routing-table=vrf_server suppress-hw-offload=no
add disabled=no distance=1 dst-address=192.168.2.0/24 gateway=Local2@vrf2 pref-src="" routing-table=vrf_server scope=30 suppress-hw-offload=no \
    target-scope=10

To achieve successful DHCP-server - DHCP-relay communication we should add NAT rules:

/ip firewall nat
add action=dst-nat chain=dstnat dst-address=192.168.2.1 dst-port=67 in-interface=To-DHCP-Server protocol=udp src-address=192.168.0.1 to-addresses=\
    192.168.0.2
add action=dst-nat chain=dstnat dst-address=192.168.1.1 dst-port=67 in-interface=To-DHCP-Server protocol=udp src-address=192.168.0.1 to-addresses=\
    192.168.0.2