6.41rc61: DHCP server ignores dns-servers?

RouterOS General
1

Hi,

Under “/ip dhcp-server network” I have my LAN network configured with “dns-server=8.8.8.8”, but RouterOS is completely ignoring that and advertising its own IP address plus the gateway’s IP address as domain servers.

Yes, I know for most LANs that would be normal, but then what’s the point of that dns-server parameter? If I have it set to 8.8.8.8, I really expect the actual offers to have 8.8.8.8 in them.

I’m fairly sure it used to work in previous versions. But I don’t know how to downgrade to rc56 and check…

> /ip dns print 
                      servers: 8.8.8.8,8.8.4.4
              dynamic-servers: 192.168.1.254
        allow-remote-requests: yes

…

> /ip dhcp-server network export
add address=192.168.1.0/24 dns-server=8.8.8.8 gateway=192.168.1.254

…

> /log print
06:15:22 dhcp,debug,packet homelan sending offer with id 4235275550 to 192.168.1.65
.....
06:15:22 dhcp,debug,packet     Subnet-Mask = 255.255.255.0 
06:15:22 dhcp,debug,packet     Router = 192.168.1.254 
06:15:22 dhcp,debug,packet     Domain-Server = 192.168.1.37,192.168.1.254

(.37 is the mikrotik DHCP server, .254 is the gateway router)

2

Hi,

I have the same problem here. DHCP Server is offering DNS servers configured under “/ip dns”

/ip dns print
servers: 9.9.9.9,8.8.8.8,8.8.4.4and NTP servers configured under “/system ntp client”
/system ntp client print
enabled: yes
mode: unicast
primary-ntp: 192.168.1.2instead of them configured under for the network “/ip dhcp-server network”
/ip dhcp-server network print value-list
address: 192.168.1.0/24
gateway: 192.168.1.1
netmask: 24
dns-server: 192.168.1.2,192.168.1.3,192.168.1.4
wins-server:
ntp-server: 192.168.1.250
caps-manager:
domain:
dhcp-option:
Log example:
20:52:29 dhcp,debug,packet lan received request with id 2733563153 from 0.0.0.0
20:52:29 dhcp,debug,packet ciaddr = 0.0.0.0
20:52:29 dhcp,debug,packet chaddr =
20:52:29 dhcp,debug,packet Msg-Type = request
20:52:29 dhcp,debug,packet Address-Request = 192.168.1.50
20:52:29 dhcp,debug,packet Parameter-List = Subnet-Mask,Broadcast-Address,Unknown(2),Classless-Route,Domain-Name,Domain-Server,Host-Name,Unknown(40),Unknown(41),NTP-Server,Interface-MTU,Domain-Search,Router
20:52:29 dhcp,debug,packet Client-Id =
20:52:29 dhcp,debug,packet lan sending ack with id 2733563153 to 192.168.1.50
20:52:29 dhcp,debug,packet ciaddr = 0.0.0.0
20:52:29 dhcp,debug,packet yiaddr = 192.168.1.50
20:52:29 dhcp,debug,packet siaddr = 192.168.1.1
20:52:29 dhcp,debug,packet chaddr =
20:52:29 dhcp,debug,packet Msg-Type = ack
20:52:29 dhcp,debug,packet Server-Id = 192.168.1.1
20:52:29 dhcp,debug,packet Address-Time = 864000
20:52:29 dhcp,debug,packet Subnet-Mask = 255.255.255.0
20:52:29 dhcp,debug,packet Domain-Name = “”
20:52:29 dhcp,debug,packet Domain-Server = 192.168.1.1,9.9.9.9,8.8.8.8,8.8.4.4
20:52:29 dhcp,debug,packet NTP-Server = 192.168.1.2
20:52:29 dhcp,debug,packet Router = 192.168.1.1Any ideas?

3

Same issue here, router is announcing its ip + dynamic pppoe dns servers instead of the configured dns-server.
Redid the configuration about three times until I recognized that it must be a RC bug…

(Ugly but working) temporary solution would be a firewall dnat rule or just a forward-reject like this if the router should be the only dns server:

/ip firewall filter add action=reject chain=forward comment="reject dns forward (dhcp seems broken\?)" dst-port=53 in-interface=LAN-Bridge out-interface=VDSL protocol=udp reject-with=icmp-network-unreachable place-before=0
4

Hi! I can confirm this issue too. I have choosen the simplest solution and have reverted back to v6.41rc56 which works fine. I hope this issue will be fixed in the next RC.

5

Confirm.
DNS servers from router’s /ip dns settings servers are “magicaly forwarded” to hosts in my network.

6

the patch will be?

7

This also happens to me when I am testing LTE IP passthrough feature.

Sent from my SM-G935F using Tapatalk

8

I hope this isn’t some “new direction for simplified configuration”…
It always has been like this (bad!) for IPv6, where the router advertises its own configured IPv6 DNS servers on the local network,
with no way at all to customize this (e.g. advertising the router itself as DNS server or some other DNS server on internet).

In IPv4 it worked as it should until now, but apparently it is now broken.
I think when MikroTik want to offer the capability to just relay some information (DNS, NTP) in the DHCP reply, it should
be a configurable option (can be ON by default), but it should be possible to override it with configured information as it was
before on the IPv4 DHCP server.

9

Has anybody tested if is is working again in final 6.41?

I’m a little bit scared of testing it, because i could’nt find anything related to this in the changelog.

10

Yes, it is working again in 6.41 :slight_smile: