How can i create Virtual Gateways

If you are using all the 4 NICs already, try terminating 3 ISPs in to seperate VLANS change the NIC 2 to any custom zone (could be your LAN or DMZ) and add VLANS to each of the ISP under the WAN zones you should be able to achieve what you need.

Thanks Kranthiyadlapudi .
but what if i am not using VLANS . it is just a small 4 NIC Device . is there is any other way to add multi GW for those IP aliases ? i mean it sound very simple feature.

so? any advice how to achive this ?

Kranthi Yadlapudi :) . is there any other way to do this without going to VLANs ?
Thanks

You can only have one gateway, you need to setup routing to use the ISP services on the other ports.
There are exceptions to this rule and that is if you have multiple internal networks that need to go the these ports and not others.
Think about how the packets would know where to go if you have one internal network and 3 external networks each with their own gateway?

ian