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Date: Mon, 09 Feb 2015 17:00:28 +0000
From: Paul Thornton <prt@prt.org>
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To: freebsd-net@freebsd.org
Subject: Re: ifconfig greX create disables IPv6 forwarding
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On 09/02/2015 16:34, Daniel Corbe wrote:
>
> For some reason, every time I create a GRE interface on a FreeBSD IPv6
> gateway, net.inet6.ip6.forwarding is disabled.  As long as I manually
> re-enable it with sysctl, both the GRE tunnel and the IPv6 network
> behind this machine will continue to work; however, it's certainly far
> from ideal.
I stumbled acro

I discovered this in January.  See this thread:

http://lists.freebsd.org/pipermail/freebsd-net/2015-January/040797.html

Are you enabling forwarding using ipv6_gateway_enable in rc.conf, or are 
you just setting net.inet6.ip6.forwarding to 1 in sysctl.conf?

devd gets involved running /etc/rc.d/netif start and that seems to check 
(and set) the forwarding sysctls based on the rc.conf entries - so if 
you've set them "manually" they get reset when a new interface is 
brought up.

Adding ipv6_gateway_enable="YES" in /etc/rc.conf should fix this.

Paul.