Hi,
here is my little routing problem. I have the RB750GL connected to subnet(192.168.128.0/24) on interface three. Finally there are three devices in the subnet:
ISP Telekom DSL modem 192.168.128.240
VM Win XP 192.168.128.90
RB750GL port 3 192.168.128.254
The mikrotik device works as a dhcp server which supplies the gateway IP 192.168.128.254. I have another ISP in a second subnet. Because of this the RB750GL works as a central router controlling the internet access. Now the internet traffice from subnet 192.168.128.0/24 should use the Telekom modem as gateway. My default internet gateway is therefore located in the second subnet.
Without any mangle/routing rules all internet traffic is forwarded to the second subnet with its default internet gateway. But as I said subnet 192.168.128.0/24 should use the Telekom DSL modem as gateway. So I must tell all packets arriving at port 3 with destination internet to use the telekom modem as gateway.
I tried the following:
/ip firewall mangle
add action=mark-connection chain=prerouting comment=
“Mark connection ::: each new connection ::: incoming from ‘ether3’”
connection-state=new disabled=no in-interface=ether3_telekom
new-connection-mark=conn_Telekom passthrough=yes src-address=
192.168.128.0/24
add action=mark-routing chain=prerouting comment=“Place a router tag for packe
ts from Telekom Subnet and destination internet.” connection-mark=
conn_Telekom disabled=no new-routing-mark=fromTelekomSubnetToWWW
passthrough=yes src-address=192.168.128.0/24
/ip route
add check-gateway=ping comment=“----- Internet over Telekom -----” disabled=
no distance=1 dst-address=0.0.0.0/0 gateway=192.168.128.240 routing-mark=
fromTelekomSubnetToWWW scope=30 target-scope=10
What works correctly:
- ping/nslookup works well
- Tracert is also possible by using the Telekom GW
What does NOT work:
- IE Browser cannot open any webpage
- All other programs don’t have internet access
Why can’t I open webpages etc. but ping works?! 
Thanks for your help!
Regards Toby