opnsense box not pinging anything on the internet. But internet works!

[geek]

So in summary:

Client's on OPNSENSE LAN -> can ping the WAN router (192.168.1.1)
Opnsense BOX (192.168.1.2) -> CANNOT ping the WAN router (192.168.1.1)

Funny part is -> UDP comms work, but ICMP does not. See attached.

I am convinced its the ISP's router that's the problem

[cookiemonster]

Both WAN and LAN are on RFC1918 networks? Maybe bogons rule is blocking.

Yes. Because the ISPs are shitty and whenever there's a problem, they'll lay the blame on "your firewall" if something goes wrong. So we do it like this (I know Double Nat, bad practice etc...  )

Both Bogons and Private IP Blocks are disabled

OK, makes sense now.

So in summary:

Client's on OPNSENSE LAN -> can ping the WAN router (192.168.1.1)
Opnsense BOX (192.168.1.2) -> CANNOT ping the WAN router (192.168.1.1)

Funny part is -> UDP comms work, but ICMP does not. See attached.

I am convinced its the ISP's router that's the problem

Very likely imho. A packet capture would probably confirm it.

[CJ]

My next step was to suggest a packet capture.