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Mikrotik always request ip from dhcp server

Posted: Mon Aug 14, 2017 2:29 pm
by Mimiko
Hello.
I've disabled DHCP Client and set a static IP. Mikrotik is serving on static IP. But it always once a minute sends DHCP Request to local DHCP server. This mikrotik is not configured to be a DHCP server, nor a DHCP relay. Where to search why it sends DHCP Requests?

Thank you.

Re: Mikrotik always request ip from dhcp server

Posted: Tue Aug 15, 2017 7:48 am
by sjwrick
So does it actually get an IP from the DHCP server?

Does the DHCP server see the request and the associated MAC address definitely belongs to the Mikrotik in question?

Rick

Re: Mikrotik always request ip from dhcp server

Posted: Tue Aug 15, 2017 9:14 am
by Mimiko
Yes, server sees request and offer an IP (same one for the Mikrotik's MAC). But it is not used by Mirkotik. It has a static different IP.
Doing packet sniffing I see that this DHCP Requests Mikrotik send on all configured vlans.

Re: Mikrotik always request ip from dhcp server

Posted: Tue Aug 15, 2017 5:19 pm
by doneware
can you post the captures you did on the mikrotik (just go with ip-protocol=udp port=67,68)
normally the router shall not be sending no dhcp requests, even the default configuration is running dhcp client on external interface only (e.g. ether1).

Re: Mikrotik always request ip from dhcp server

Posted: Wed Aug 16, 2017 9:46 am
by Mimiko
This is the capture. As filtered is on src mac, there is not responce packets. Packet capturing is done on all interfaces.
dhcp mikrotik.gif

Re: Mikrotik always request ip from dhcp server

Posted: Wed Aug 16, 2017 7:14 pm
by doneware
This is the capture. As filtered is on src mac, there is not responce packets. Packet capturing is done on all interfaces.
ok, that tells me that your device is sending out dhcp requests on 3 different bridge interfaces
- bridge-default
- bridge-berd
- bridge-voip

the rest of the capture can be ignored as those are the same packets seen on the VLAN subif and the outgoing dot1q trunk.
would you mind to save the pcap as file and attach it to the post so i can look at the contents of the packets?
all in all it doesn't look like too good if you don't have no DHCP-client entries in your config.

Re: Mikrotik always request ip from dhcp server

Posted: Wed Aug 16, 2017 9:00 pm
by pe1chl
Did you configure alerts on the IP->DHCP server page?

Re: Mikrotik always request ip from dhcp server

Posted: Thu Aug 17, 2017 8:04 pm
by Mimiko
Did you configure alerts on the IP->DHCP server page?
You are a genius. Yes. I've configured alerts to detect dhcp servers. Thank you very very.

Problem solved.

Is there a way to change the time between dhcp checking?