I'm pretty new to networking and firewalls configurations.
Basically I replaced the old sysadmin in my company, and I didn't get too much information about the firewalls and the network.

This is our network topology pretty much:

( we have our own hosted cabinet in a datacenter )

So, Datacenter Internet > 3Com Switch > physical pfSense Firewall > Dell Switch > All other servers.

Now, I'm trying to install a new virtual pfsense firewall.

I connected 1 of the ESXi ports to the 3Com Switch and the other port to the Dell Switch.

now, created a pfsense VM with 2 NIC's, WAN & LAN, assigned the NIC's to the right WAN.

I have range of IP's the datacenter assigned for us:

( Just an example )

10.0.0.1/248 - 6 IP's

So I tried to configure the WAN interface IPv4 with 10.0.0.3, and set the gateway as 10.0.0.4.

( My physical firewall also uses 10.0.0.4 as gateway ).

It doesn't work on the VM, just no internet and it shows the gateway as 'Offline'.
I also cannot ping 8.8.8.8 or anything.

might be a stupid question but can't I configure any IP of the range I have as a gateway?

I guess I'm missing something but I have no clue what.