Connecting two different network ranges

RouterOS General
1

Hello,

i have connected my MT device to an existing network. It should become a bridge to that network for clients connected only via wlan or eth2-eth4.

The existing external network has the following parameters:
IP-Range 10.90.20.0/24
Gateway is on 10.90.20.1
No DHCP in network (only static ips).

The connected unit should be realized as follows:
IP: 10.90.20.38 on external network, 192.168.0.1 for clients
Dhcp Range for WLAN and eth2-eth4: 192.168.0.100 - 192.168.0.200

The existing LAN is connected to eth1 port of Mikrotik device (WAN).

Now, all clients connected to Mikrotik device should be able to access all machines in the external network (10.90.20.0) and be able to connect to internet which is served by external network from gateway.

If I try to ping the gateway (10.90.20.1) or any other machine from the MT itself (Tools->Ping) it works.
But when I connect a PC to WLAN and try to ping the gateway it fails.

I guess there is a route missing ? Or maybe a problem with NAT or routing protocol ?

It`s very exciting to play around but now I am running out of ideas. Please help ! Thank you very much !

Here is my very basic config:

# jan/02/1970 00:11:57 by RouterOS 6.41.3
# software id = U9N0-1U5X
#
# model = RouterBOARD 941-2nD
# serial number = 8ACF08FED6E6
/interface bridge
add fast-forward=no name=bridge1
/interface wireless
set [ find default-name=wlan1 ] ssid=MikroTik
/interface wireless security-profiles
set [ find default=yes ] supplicant-identity=MikroTik
/ip pool
add name=pool1 ranges=192.168.0.100-192.168.0.200
/ip dhcp-server
add address-pool=pool1 disabled=no interface=bridge1 name=server1
/interface bridge port
add bridge=bridge1 interface=wlan1
add bridge=bridge1 interface=ether2
add bridge=bridge1 interface=ether3
add bridge=bridge1 interface=ether4
/ip address
add address=10.90.20.38/24 interface=ether1 network=10.90.20.0
add address=192.168.0.1/24 interface=bridge1 network=192.168.0.0
/ip dhcp-server network
add address=192.168.0.0/24 dns-server=192.168.0.1 gateway=192.168.0.1
/ip dns
set servers=192.168.0.1
/ip route
add distance=1 gateway=10.90.20.1
2

What you are missing is the following firewall rule:

/ip firewall nat
add chain=srcnat action=src-nat out-interface=ether1 to-addresses=10.90.20.38

And there is one mistake, you are telling the Mikrotik to use itself as a DNS:

/ip dns
set servers=192.168.0.1

So use an address of some DNS server in the existing network, otherwise Weird Things will happen.

A technical remark, the word “bridge” has a certain meaning in networking, so this Mikrotik will definitely not be a “bridge” to the existing network.