Re: GRE tunnel and a ipv4 subnet /29

From: Eugene Grosbein <>
Date: Fri, 11 Mar 2022 23:10:39 UTC
12.03.2022 5:45, Jack Raats wrote:

> I have an ipv4 test subnet from extraip 37.x.y.0/29
> My internet connection has ip-address a.b.c.d.
> I've a Fritxbox router and behind NAT is my FreeBSD server with ip-address
> On this router I've opened the firewall for GRE to my FreeBSD server.
> On my FreeBSD server rc.conf has the following lines:
> cloned_interfaces=“gre0”
> ifconfig_gre0=“inet 37.x.y.2 37.x.y.1 netmask tunnel a.b.c.d gatewayip”
> static_routes=“tunnel”
> route_tunnel=“37.x.y.0/29 37.x.y.1”
> This doesn't work. Whats wrong? Do I forget something?

You cannot use 37.x.x.2 for any interface on FreeBSD unless your upstream router (Fritxbox)
delivers packets to this IP address to FreeBSD *without* NAT.

Create static route for 37.x.x.2/32 with gateway address in the routing table of Fritxbox.
If you enabled NAT-based forwarding of GRE protocon on Fritxbox, disable it. Then it should work.