Hi everyone,
I am using a RouerBoard RB450G with RouterOS v5.0.
I set up a DHCP Server on interface ether3 and it works fine.
However, when I check the log I notice 2 problems as you can see in the pictures.




1. dhcp warning dhcp1 offering lease 10.0.10.69 for 00:23:14:52:B4:B4 to B8:AC:6F:63:03:7C without success

This only happens to one IP and two MAC as above.

2. DHCP Server deassigned and assigned an IP at a same time.

12:27:20 dhcp1 deassigned 10.0.10.62 from 00:0D:0B:B9:27:01
12:27:20 dhcp1 assigned 10.0.10.62 to 00:0D:0B:B9:27:01

This happens to some IPs and MAC addresses.

3. An IP is assigned and deassigned many times in a short time.






Here is the DHCP Server Config

add address-pool=dhcp_pool1 authoritative=after-2sec-delay bootp-support=static disabled=no interface=ether3-local lease-time=2d name=dhcp1

/ip dhcp-server config
set store-leases-disk=5m

/ip dhcp-server network
add address=10.0.0.0/16 dns-server=8.8.8.8,210.245.24.22,203.162.4.1,203.162.4.190,208.67.222.222 gateway=10.0.10.1

Here is the Interface ether3

mac-address=00:0C:42:A2:98:2F master-port=none mtu=1500 name=ether3-local speed=100Mbps
set 3 arp=enabled auto-negotiation=yes bandwidth=unlimited/unlimited disabled=no full-duplex=yes l2mtu=1524


So I hope I can have an explanation about why this happen and how could I fix this.
Thank you very much.

I would start by going to the logging settings and enable dhcp debug for better logging. you may have to forward it to a syslog server as it may have too much info for the mikrotik log to show properly.

/system logging
add action=memory disabled=yes prefix=dhcp topics=debug

I have the same issue and can't make support.rif --> Couldn't perform action - not permitted (9)

ROS 5.4

Tried the filter rules, but none worked for me.

Not sure how to do code so someone else can translate if they like but here's what worked for me:

SOLUTION (on 5.4): IP --> DHCP Server --> Leases --> Add new --> General="Pool_Name", MAC Address="MAC address of desired blocked", Server="Name of DHCP Server failing", Block access = yes, Address List = Black-list

Hope that helps someone else