DHCP client has a possibility to set up options that are sent to DHCP server. For example, hostname and MAC address. Syntax is same as for [[Manual:IP/DHCP_Server#DHCP_Options|DHCP server options]].
{{Note| This feature is available since RouterOS 6.0}}
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:
{|
!|Name
!|code
!|value
|-
||clientid_duid
||61
||0xff$(CLIENT_DUID)
|-
||clientid
||61
||0x01$(CLIENT_MAC)
|-
||hostname
||12
||$(HOSTNAME)
|}
===IPv6===
===IPv6===
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Starting from v5.8 DHCP Client can receive delegated prefixes from DHCPv6 server.
Starting from v5.8 DHCP Client can receive delegated prefixes from DHCPv6 server.
Currently received prefix is added to IPv6 pool, which later can be used for example in pppoe server configuration.
Currently received prefix is added to IPv6 pool, which later can be used for example in pppoe server configuration.
Starting from v5.9, DHCPv6 client configuration was moved to /ipv6 sub-menu. [[M:IPv6/DHCP_Client | <code>Read-more >></code>]]
==Quick setup example==
==Quick setup example==
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</pre>
</pre>
After interface is added, you can use rint" or "print detail" command to see what parameters DHCP client acquired:
After interface is added, you can use "print" or "print detail" command to see what parameters DHCP client acquired:
<pre>
<pre>
[admin@MikroTik] ip dhcp-client> print detail
[admin@MikroTik] ip dhcp-client> print detail
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{{Mr-arg-table
{{Mr-arg-table
|arg=add-default-route
|arg=add-default-route
|type=yes {{!}} no
|type=yes {{!}} no {{!}} special-classless
|default=yes
|default=yes
|desc=Whether to install default route in routing table received from dhcp server.
|desc=Whether to install default route in routing table received from dhcp server. By default RouterOS client complies to RFC and ignores option 3 if classless option 121 is received. To force client not to ignore option 3 set ''special-classless''. This parameter is available in v6rc12+
* '''yes''' - adds classless route if received, if not then add default route (old behavior)
* '''special-classless''' - adds both classless route if received and default route (MS style)
}}
}}
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{{Mr-arg-table
{{Mr-arg-table
|arg=default-route-distance
|arg=comment
|type=integer:0..255
|type=string
|default=
|default=
|desc=Distance of default route. Applicable if <code>add-default-route</code> is set to <code>yes</code>.
|desc=Short description of the client
}}
}}
{{Mr-arg-table
{{Mr-arg-table
|arg=host-name
|arg=default-route-distance
|type=string
|type=integer:0..255
|default=
|default=
|desc=Host name of the client sent to a DHCP server. If not specified, client's system identity will be used.
|desc=Distance of default route. Applicable if <code>add-default-route</code> is set to <code>yes</code>.
}}
}}
{{Mr-arg-table
{{Mr-arg-table
|arg=ipv4
|arg=disabled
|type=yes {{!}} no
|type=yes {{!}} no
|default=yes
|default=yes
|desc=Client will receive IPv4 address from the server if this parameter is set.
|desc=
}}
}}
{{Mr-arg-table
|arg=ipv6-pd
|type=yes {{!}} no
|default=no
|desc=Client will receive delegated prefix from [[M:IP/DHCP_Server#IPv6 | DHCPv6-PD server]].
}}
{{Mr-arg-table
{{Mr-arg-table
|arg=pool-name
|arg=host-name
|type=string
|type=string
|default=
|default=
|desc=Name of the [[M:IPv6/Pool | IPv6 pool]] in which received IPv6 prefix will be added. Applicable if '''ipv6-pd''' is enabled.
|desc=Host name of the client sent to a DHCP server. If not specified, client's system identity will be used.
}}
}}
{{Mr-arg-table
{{Mr-arg-table
|arg=pool-prefix-length
|arg=interface
|type=string
|type=string
|default=
|default=
|desc=Prefix length parameter that will be set for [[M:IPv6/Pool | IPv6 pool]] in which received IPv6 prefix is added. Applicable if '''ipv6-pd''' is enabled. Prefix length must be greater than the length of received prefix, otherwise prefix-length will be set to received prefix length + 8 bits.
|desc=Interface on which DHCP client will be running.
}}
}}
{{Mr-arg-table
{{Mr-arg-table
|arg=interface
|arg=script
|type=string
|type=script
|default=
|default=
|desc=Interface on which DHCP client will be running.
|desc=Execute script on status change. This parameter is available in v6.39rc33+ These are available variables that are accessible for the event script:
* <var>bound</var> - 1 - lease is added/changed; 0 - lease is removed
* <var>server-address</var> - server address
* <var>lease-address</var> - lease address provided by server
* <var>interface</var> - name of interface on which client is configured
* <var>gateway-address</var> - gateway address provided by server
* <var>vendor-specific</var> - stores value of option 43 received from DHCP server
* <var>lease-options</var> - array of received options
* '''searching''' - sending "solicit" and trying to get "advertise"
* '''requesting''' - sent "request" waiting for "reply"
* '''bound''' - received "reply". Prefix assigned.
* '''renewing''' - sent "renew", waiting for "reply"
* '''rebinding''' - sent "rebind", waiting for "reply"
* '''error''' - reply was not received in time or some other error ocurred.
* '''stopping''' - sent "release"
}}
}}
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}}
}}
==Examples==
===Lease script example===
Since RouterOS v6.39rc33, it is possible to execute a script when DHCP client obtains new lease or loses existing. This is an example script that automatically adds a default route with routing-mark=WAN1 and removes it when the lease expires or is removed.
\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"
</pre>
===Resolve default gateway when 'router' (option3) is from different subnet===
In some cases administrators tend to set 'router' option which cannot be resolved with offered IP's subnet.
For example, 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 unresolved default route:
<pre>
# 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
</pre>
To fix this we need to add /32 route to resolve the gateway over ether1, which can be done by running script below each time DHCP client gets an address
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 the DHCP client obtains one, the route obtained by the DHCP client would be shown as invalid.
RouterOS DHCP cilent asks for 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,
Option
DHCP client has a possibility to set up options that are sent to DHCP server. For example, hostname and MAC address. Syntax is same as for DHCP server options.
Note: This feature is available since RouterOS 6.0
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:
Name
code
value
clientid_duid
61
0xff$(CLIENT_DUID)
clientid
61
0x01$(CLIENT_MAC)
hostname
12
$(HOSTNAME)
IPv6
Starting from v5.8 DHCP Client can receive delegated prefixes from DHCPv6 server.
Currently received prefix is added to IPv6 pool, which later can be used for example in pppoe server configuration.
Starting from v5.9, DHCPv6 client configuration was moved to /ipv6 sub-menu. Read-more >>
Quick setup example
Add a DHCP client on ether1 interface:
/ip dhcp-client add interface=ether1 disabled=no
After interface is added, you can use "print" or "print detail" command to see what parameters 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>
Note: If interface used by DHCP client is part of VRF configuration, then default route and other received routes from DHCP server will be added to VRF routing table.
Properties
Sub-menu:/ip dhcp-client
Property
Description
add-default-route (yes | no | special-classless; Default: yes)
Whether to install default route in routing table received from dhcp server. By default RouterOS client complies to RFC and ignores option 3 if classless option 121 is received. To force client not to ignore option 3 set special-classless. This parameter is available in v6rc12+
yes - adds classless route if received, if not then add default route (old behavior)
special-classless - adds both classless route if received and default route (MS style)
client-id (string; Default: )
Corresponds to the settings suggested by the network administrator or ISP. If not specified, client's MAC address will be sent
Renew current leases. If the renew operation was not successful, client tries to reinitialize lease (i.e. it starts lease request procedure (rebind) as if it had not received an IP address yet)
Examples
Lease script example
Since RouterOS v6.39rc33, it is possible to execute a script when DHCP client obtains new lease or loses existing. This is an example script that automatically adds a default route with routing-mark=WAN1 and removes it when the lease expires or is removed.
Resolve default gateway when 'router' (option3) is from different subnet
In some cases administrators tend to set 'router' option which cannot be resolved with offered IP's subnet.
For example, 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 unresolved default route:
To fix this we need to add /32 route to resolve the gateway over ether1, which can be done by running script below each time DHCP client gets an address
