can't access web gui at 192.168.1.1

[cdaug]

I am checking out opnsense in virtual box, and have ran into a problem that I am trying to understand.

When I set the LAN interface to 192.168.1.1, I can ping the interface but trying to open the web gui times out (and there's no internet access from my client)

If I change the LAN interface to 10.0.0.1, the web gui and internet work fine.

The virtual box is setup with two vms
opnsense - 2 nics. One set to NAT (wan) and the second set to internal (lan)
ubunutu client - 1 nic set to internal (DHCP is pulling the correct addresses each time) I am opening gui / internet from here.

It's not a huge issue as NOT using 192.168.1.1 is a suitable workaround. I am just trying to understand why the gui / internet doesn't work with LAN set to this IP but works fine on others. (and honestly may be VBOX configuration issue instead)

I appreciate any ideas!

[cdaug]

I tried the same virtualbox setup with pfsense, and it worked fine. So I'm hesitant to blame virtual box.

Regardless, If anyone else has same issue with the same setup, my recommendation would be to just use 10.0.0.1 on the LAN.