Why arn't RFC1918 addresses being blocked?

[Howard2937011]

I am stumped with this one…

I thought that "Block Private Networks" on my WAN interface would block any RFC1918 addresses from leaving my LAN. I recently discovered that this is not true. When I try to access the management interface for my cable modem (192.168.100.1) from a computer on my LAN interface, it shockingly works.

What's odd, is that if I add a rule on the WAN interface to block all TCP traffic to 192.168.100.1, it doesn't seem to work:

I tried:

IPv4 TCP	192.168.100.1	*	*	*	*	none

and

IPv4 TCP	*	*	192.168.100.1	*	*	none

But neither seem to work. Also as I said, before, I checked "Block Private Networks" so this shows up on my WAN firewall rules:

 	*	RFC 1918 networks	*	*	*	*	*	 	Block private networks

Other than "Block bogon networks" I have no other WAN rules configured. Any advice would be appreciated, thanks.

[kpa]

You're misunderstanding what the option does. It is for blocking inbound connections on the WAN interface, it does not block anything coming from the LAN interface and the network attached to it.

[johnpoz]

Firewall rules are always (except for floating that can be set) as INBOUND to the interface..

[dparring]

See discussion here:

https://forum.pfsense.org/index.php?topic=103117.0

And Wiki HOWTO here:

https://doc.pfsense.org/index.php/Prevent_RFC1918_traffic_from_leaving_pfSense_via_the_WAN_interface

DP