MikroTik

Posted: **Mon Mar 12, 2012 3:18 pm**

I found out that one of my dhcp clients does not send a Parameter Request List (Option 55) in the discover packet.

In this situation, the MicroTik dhcp server does not include the Subnet Mask (Option 1) in the offer.

Other dhcp servers sends this Subnet Mask in any way, (which sounds pretty decent).

Is there a way to "force" RoterOS dhcp server to reply with Subnet Mask even though it was not requested?

Posted: **Wed Jan 15, 2014 3:15 pm**

I Have the same problem with HP t5135 thin client.

Netwoark 10.0.3.0/24
Gateway (DHCP-server, DNS, etc) is 10.0.3.100

Normal client:

echo: dhcp,debug,packet     Parameter-List = Subnet-Mask,Static-Route,Router,Domain-Server,Domain-Name,Unknown(28),Address-Time,Renewal-Time,Unknown(59)
echo: dhcp,debug,packet server1 sending ack with id 2974379535 to 10.0.3.112
echo: dhcp,debug,packet     ciaddr = 10.0.3.112
echo: dhcp,debug,packet     yiaddr = 10.0.3.112
echo: dhcp,debug,packet     siaddr = 10.0.3.100
echo: dhcp,debug,packet     chaddr = D4:22:3F:67:34:7E
echo: dhcp,debug,packet     Msg-Type = ack
echo: dhcp,debug,packet     Server-Id = 10.0.3.100
echo: dhcp,debug,packet     Address-Time = 1800
echo: dhcp,debug,packet     Subnet-Mask = 255.255.255.0
echo: dhcp,debug,packet     Router = 10.0.3.100
echo: dhcp,debug,packet     Domain-Server = 10.0.3.100

Problem client (HP thin client 5135) - "Subnet-Mask = 255.255.255.0 " string is absent.

echo: dhcp,debug,packet     Parameter-List = Unknown(180),Unknown(161),Unknown(162),Unknown(184),Unknown(185),Unknown(186),Unknown(187),Unknown(190),Unknown(202),Unknown(203),Router,Domain-Name,Domain-Server
echo: dhcp,info server1 assigned 10.0.3.156 to 00:1C:C4:8C:02:60
echo: dhcp,debug,packet server1 sending ack with id 1292734693 to 10.0.3.156
echo: dhcp,debug,packet     ciaddr = 0.0.0.0
echo: dhcp,debug,packet     yiaddr = 10.0.3.156
echo: dhcp,debug,packet     siaddr = 10.0.3.100
echo: dhcp,debug,packet     chaddr = 00:1C:C4:8C:02:60
echo: dhcp,debug,packet     Msg-Type = ack
echo: dhcp,debug,packet     Server-Id = 10.0.3.100
echo: dhcp,debug,packet     Address-Time = 1800
echo: dhcp,debug,packet     Router = 10.0.3.100
echo: dhcp,debug,packet     Domain-Server = 10.0.3.100

Have anybody any ideas?

Posted: **Wed Apr 09, 2014 6:05 pm**

I'm having this same problem, with both RouterOS v5.18 and v6.11

My DHCP server is set to "static-only" and I made static leases for my clients. They do not receive a subnet mask in dhcp offer, so they assume 255.255.0.0 instead of 255.255.255.0 which I am using:

15:00:56 dhcp,debug,packet ether3-dhcp-serv received request with id 3167770653 from 0.0.0.0 
15:00:56 dhcp,debug,packet     ciaddr = 0.0.0.0 
15:00:56 dhcp,debug,packet     chaddr = 00:25:90:D9:CF:F6 
15:00:56 dhcp,debug,packet     Msg-Type = request 
15:00:56 dhcp,debug,packet     Client-Id = 01-00-25-90-D9-CF-F6 
15:00:56 dhcp,debug,packet     Class-Id = "udhcp 1.12.0" 
15:00:56 dhcp,debug,packet     Address-Request = 172.16.12.111 
15:00:56 dhcp,debug,packet     Server-Id = 172.16.12.1 
15:00:56 dhcp,debug,packet     Parameter-List = Subnet-Mask,Router,Domain-Server,Host-Name,Domain-Name,Unknown(28),NTP-Server 
15:00:56 dhcp,info ether3-dhcp-serv assigned 172.16.12.111 to 00:25:90:D9:CF:F6 
15:00:56 dhcp,debug,packet ether3-dhcp-serv sending ack with id 3167770653 to 172.16.12.111 
15:00:56 dhcp,debug,packet     ciaddr = 0.0.0.0 
15:00:56 dhcp,debug,packet     yiaddr = 172.16.12.111 
15:00:56 dhcp,debug,packet     siaddr = 172.16.12.1 
15:00:56 dhcp,debug,packet     chaddr = 00:25:90:D9:CF:F6 
15:00:56 dhcp,debug,packet     Msg-Type = ack 
15:00:56 dhcp,debug,packet     Server-Id = 172.16.12.1 
15:00:56 dhcp,debug,packet     Address-Time = 21600 
15:00:56 dhcp,debug,packet     Domain-Server = 172.16.12.1 
15:00:56 dhcp,debug,packet     NTP-Server = 17.151.16.14,17.171.4.14

Posted: **Wed Apr 09, 2014 6:08 pm**

And if you set "netmask" in dhcp-server network configuration?

Posted: **Sat Apr 12, 2014 9:54 pm**

I was able to fix this by changing the DHCP Network "Address" field from "172.16.12.0" to "172.16.12.0/24". Both before and after, I had the "netmask" field set to "24"

MikroTik

DHCP Server does not respond with a Subnet mask

DHCP Server does not respond with a Subnet mask

Re: DHCP Server does not respond with a Subnet mask

Re: DHCP Server does not respond with a Subnet mask

Re: DHCP Server does not respond with a Subnet mask

Re: DHCP Server does not respond with a Subnet mask