MikroTik RouterOS v2.9 - Store Leases on Disk

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allowed)

• 255.255.255.255 - the DHCP server should be used for any incomming request from a DHCP

relay except for those, which are processed by another DHCP server that exists in the /ip

dhcp-server submenu

src-address ( IP address ; default: 0.0.0.0 ) - the address which the DHCP client must send

requests to in order to renew an IP address lease. If there is only one static address on the DHCP

server interface and the source-address is left as 0.0.0.0, then the static address will be used. If there

are multiple addresses on the interface, an address in the same subnet as the range of given

addresses should be used

use-radius ( yes | no ; default: no ) - whether to use RADIUS server for dynamic leases

Notes

If using both - Universal Client and DHCP Server on the same interface, client will only receive a

DHCP lease in case it is directly reachable by its MAC address through that interface (some

wireless bridges may change client's MAC address).

If authoritative property is set to yes, the DHCP server is sending rejects for the leases it cannot

bind or renew. It also may (although not always) help to prevent the users of the network to run

illicitly their own DHCP servers disturbing the proper way this network should be functioning.

If relay property of a DHCP server is not set to 0.0.0.0 the DHCP server will not respond to the

direct requests from clients.

Example

To add a DHCP server to interface ether1, lending IP addresses from dhcp-clients IP pool for 2

hours:

/ip dhcp-server add name=dhcp-office disabled=no address-pool=dhcp-clients \

interface=ether1 lease-time=2h

[admin@MikroTik] ip dhcp-server> print

Flags: X - disabled, I - invalid

# NAME INTERFACE RELAY ADDRESS-POOL LEASE-TIME ADD-ARP

0 dhcp-office ether1 dhcp-clients 02:00:00

[admin@MikroTik] ip dhcp-server>

Store Leases on Disk

Home menu level: /ip dhcp-server config

Description

Leases are always stored on disk on graceful shutdown and reboot. If on every lease change it is

stored on disk, a lot of disk writes happen. There are no problems if it happens on a hard drive, but

is very bad on Compact Flash (especially, if lease times are very short). To minimize writes on disk,

all changes are flushed together every store-leases-disk seconds. If this time will be very short

(immediately), then no changes will be lost even in case of hard reboots and power losts. But, on

CF there may be too many writes in case of short lease times (as in case of hotspot). If this time will

be very long (never), then there will be no writes on disk, but information about active leases may

be lost in case of power loss. In these cases dhcp server may give out the same ip address to another

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