IPv4/IPv6 over the same IPv4 GRE tunnel

  • I'm trying to setup a GRE tunnel between pfSense and a Cisco router. The WAN connection is IPv4 only. The GRE tunnel shall carry both IPv4 and IPv6 traffic. In my previous setup, with a Cisco router on my site as well, I could easy define one tunnel interface with both IPv4 and IPv6 adressess. Now, with pfSense on my site, as I understand it, I can't do that so I created two GRE interfaces (OPT1/OPT2). One with the IPv4 link addresses and one with the IPv6 link addresses.

    This worked fine until I upgraded to 2.3.0. Now, the IPv6 GRE tunnel (gre1/OPT2) is stuck in "pending" state and no IPv6 traffic if sent or received.

    I noticed, when showing the interface status, that the IPv6 GRE interface (gre1/OPT2) is not showing the correct MTU size and IPv6 netmask as configured on the interface. I'm not sure however, if this is something that would be resolved if the GRE tunnel was "up".

    Any hints are greatly appreciated… Thanks!


  • Running both IPv4 and IPv6 over the same IPv4 only GRE tunnel actually seems to work over the same tunnel now! The IPv6 link-local addresses that are set on the IPv4 GRE tunnel works fine to use as p2p link for IPv6 traffic. I needed to set the remote IPv6 link-local address as IPv6 default gateway, then everything started working.

    Remote end (Cisco router) is using static IPv6 routing with the Tunnel interface as route, thus using all available IPv6 addresses to route the traffic to pfsense, including the pfsense link-local address on the GRE interface.



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