Default Gateway on different VMkernal

Hello,

We have one physical server with 2 nic cards and running ESXi 5.1 Enterprise version. Now we need to configure one nic for Internal network (Internal) and one for DMZ zone on firewall (DMZ). The DMZ nic will be connected directly on DMZ interface of Firewall and Internal nic will be connected on internal switch. I have created Standard vSwitch0 with VMkernal for Internal nic with Internal subnet and gateway. Another vSwitch1 is created with VMkernal for DMZ nic with DMZ IP. But the issue is the default gateway is only for internal gateway. I need to know how we can assign separate default gateway for DMZ vSwitch VMkernal.

Please advise.

Thanks