If you want to use multiple WANs on the same network, you need multiple WAN ports on the router that will control that network. This will not be done cheaply as it will require a business grade router. You can however configure a computer as a router and use multiple NICs, but the setup/configuration is not for the faint of heart. The typical configuration that most companies want when they set this up is to have a balanced load (connections out of the network get routed to a given circuit based on the overall load on each circuit). This does not mean you will get shared bandwidth between the two circuits, they are still two separate circuits and each connection out will use one or the other, not both. The other common configuration is a fail-over, where one is primary and is always used until it goes down, then the router hands all traffic over to the secondary until the primary is brought back up.
RouterOS config samples:
To specify IPs on an interface:
ip address
add address=192.168.3.0/24 network=192.168.0.0 broadcast=192.168.3.255 interface=Local
add address=192.168.1.0/24 network=192.168.1.0 broadcast=192.168.1.255 interface=WAN1
add address=192.168.2.0/24 network=192.168.2.0 broadcast=192.168.2.255 interface=WAN2
To Add DHCP for your LAN:
/ip dhcp-client add interface=Local disabled=no
/ip pool add name="default-dhcp" ranges=192.168.3.50-192.168.3.150;
/ip dhcp-server
add name=default address-pool="default-dhcp" interface=bridge-local disabled=no;
/ip dhcp-server network
add address=192.168.3.0/24 gateway=192.168.3.1 dns-server=192.168.3.1 comment="default configuration";
Load Balancing:
/ip firewall mangle
add chain=input in-interface=WAN1 action=mark-connection new-connection-mark=WAN1_conn
add chain=input in-interface=WAN2 action=mark-connection new-connection-mark=WAN2_conn
add chain=output connection-mark=WAN1_conn action=mark-routing new-routing-mark=to_WAN1
add chain=output connection-mark=WAN2_conn action=mark-routing new-routing-mark=to_WAN2
add chain=prerouting dst-address=192.168.1.0/24 action=accept in-interface=Local
add chain=prerouting dst-address=192.168.2.0/24 action=accept in-interface=Local
add chain=prerouting dst-address-type=!local in-interface=Local per-connection-classifier=src-address:2/0 action=mark-connection new-connection-mark=WAN1_conn passthrough=yes
add chain=prerouting dst-address-type=!local in-interface=Local per-connection-classifier=src-address:2/1 action=mark-connection new-connection-mark=WAN2_conn passthrough=yes
add chain=prerouting connection-mark=WAN1_conn in-interface=Local action=mark-routing new-routing-mark=to_WAN1
add chain=prerouting connection-mark=WAN2_conn in-interface=Local action=mark-routing new-routing-mark=to_WAN2
/ip route
add dst-address=0.0.0.0/0 gateway=192.168.1.1 routing-mark=to_WAN1 check-gateway=ping
add dst-address=0.0.0.0/0 gateway=192.168.2.1 routing-mark=to_WAN2 check-gateway=ping
add dst-address=0.0.0.0/0 gateway=192.168.1.1 distance=1 check-gateway=ping
add dst-address=0.0.0.0/0 gateway=192.168.2.1 distance=2 check-gateway=ping
/ip firewall nat
add chain=srcnat out-interface=WAN1 action=masquerade
add chain=srcnat out-interface=WAN2 action=masquerade
possible duplicate of Taking advantage of two broadband links
– Linker3000 – 2011-09-01T18:39:27.743@Linker, this differs in that he isn't asking about MLPPP (as far as I know, he was not specific about ISPs and connection types) but he was specific about the router and config he wanted, which is close to the one that the above link links to, but I think it should remain open as this is specific to RouterOS. – MaQleod – 2011-09-02T01:02:02.480