Losing connection when LAN is setup

[paradox55]

Hi all,

I have a weird setup, but with my small network I can't justify running a dedicated opnsense box.

VPS (opnsense) -> Server -> Switch -> Router (DHCP) -> WAN

What I'm trying to do is the following:

VPS (opnsense+DHCP) -> Server -> Switch -> Router (DHCP) -> WAN

The server only has one NIC, the VPS has two separate virtual nics with their own mac addresses. What I want is for everything behind the switch to be using the opnsense dhcp server and leave the coax cable tv boxes on the FIOS router.

However, upon configuring the LAN interface with services -> DHCP enabled the VPS loses all internet connectivity.

I think it's from both DHCP servers conflicting with one another. Any suggestions on how to make this setup work? And yes I can buy another NIC card if the virtual nic's won't work on this setup.

FIOS router - 192.168.1.1/24
Opnsense - 192.168.1.15 DHCP WAN
Opnsense - 172.0.0.1/8 DHCP LAN

[hbc]

Both virtual nics use the same physical nic? With or without vlans? Is your switch vlan capable?

[paradox55]

No, the switch is not vlan capable.

After testing some more it does function correctly when the FIOS router's DHCP is disabled.

Mmm. Looks like I can't do both without vlan functionality.

[hbc]

Without vlans, it's just one layer 2 segment and both dhcp servers respond to client requests. The faster response wins.
And without vlans you can switch networks just by changing ip address. With a sniffer, you get broadcasts from lan devices, can see the used subnet and just have to set a free ip. Then you switched from wan to lan ...without filtering on any firewall.

Buy a second nic, attach your modem/router with crossover cable directly to firewall on wan and connect first nic with switch.
Then it's separated on all layers.