6.41rc61: DHCP server ignores dns-servers?

g22113 · Thu Dec 07, 2017 10:48 am

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)

toxiczka · Thu Dec 07, 2017 10:10 pm

Hi,

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

Code: Select all

> /ip dns print

servers: 9.9.9.9,8.8.8.8,8.8.4.4

and NTP servers configured under "/system ntp client"

Code: Select all

> /system ntp client print 

enabled: yes

mode: unicast

primary-ntp: 192.168.1.2

instead of them configured under for the network "/ip dhcp-server network"

Code: Select all

/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:

Code: Select all


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 = 192.168.1.1

Any ideas?

lukas2511 · Fri Dec 08, 2017 2:56 am

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

Zloy2452 · Fri Dec 08, 2017 4:19 pm

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.

RafGan · Sat Dec 09, 2017 2:43 am

Confirm.
DNS servers from router's /ip dns settings servers are "magicaly forwarded" to hosts in my network.

edinorog · Tue Dec 12, 2017 5:13 am

the patch will be?

ranpha · Tue Dec 12, 2017 9:04 am

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

Sent from my SM-G935F using Tapatalk

pe1chl · Sun Dec 17, 2017 12:44 pm

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.

toxiczka · Wed Jan 03, 2018 8:08 pm

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.

RafGan · Thu Jan 04, 2018 12:11 am

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.

Yes, it is working again in 6.41

6.41rc61: DHCP server ignores dns-servers?

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