OpenVPN and Deutsche Glasfaser - IPV6 and CGNAT blocking connection?
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Hello everyone, I am struggling to get OpenVPN running on my PFSense firewall. This is something I managed a couple of years back with no problems, but now I get no reaction at all from my pfsense. I followed the instructions carefully working through the wizard and still nothing. None of the clients I tried (Android OpenVPN and Tunnelblick on Mac) get any response at all, packet capture on the firewall shows nothing on 1194, all configuration settings look fine. This really should work.
Since I got OpenVPN working last a few things have changed, one of them is my internet provider - switched from Deutsche Telekom to Deutsche Glasfaser and now I read that DG use IPV6 internally with CGNAT to give an IPV4 address in the 100.xxx.yyy.zzz range. These 100.xxx addresses are not accessible from the internet. I say that like I know what it means, which I half do. PFSense shows the WAN address is indeed a 100.x.y.z.
Putting these two together - I have got OpenVPN working before and now I get absolutely nothing and a hint of an issue from my internet provider - I am wondering if my internet provider and IPV6 may be playing a role in confounding my OpenVPN setup? If so, how do I fix it?
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If you have CGNAT you can't make inbound connections to it from the outside. The inbound connections would never reach the firewall. If the connection never reaches the firewall there is nothing for it to do.
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Many thanks for the reply - so that means if the provider uses CGNAT then I am SOOL? No chance to get OpenVPN connections working?
I did some more digging round this topic and found this - I followed through the points best I can and now get packets arriving at the WAN:
23:30:32.743269 IP 100.69.223.179.18813 > 94.31.96.153.1194: UDP, length 54 23:30:34.902711 IP 100.69.223.179.18813 > 94.31.96.153.1194: UDP, length 54However the server still does not manage to respond. Perhaps now this is an internal problem - but with this IPV4 & IPV6 stuff I am completely out of my depth. Any help gratefully received.
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Which one of those is your WAN address? The 100.69.223.179 is a CGNAT address but that indicates an outbound connection being attempted by an OpenVPN client on your node, not an inbound connection to an OpenVPN server on your node.
Outbound clients should work fine. Your problem will be connecting inbound.
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You are right, I realised my mistake just after posting - the PC attempting the OpenVPN connection was inside the LAN. The WAN address is 100.69.223.179. This starts to explain why my phone on its data connection cannot reach the WAN at all.
What can be done to get OpenVPN working again?
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@charry2014 said in OpenVPN and Deutsche Glasfaser - IPV6 and CGNAT blocking connection?:
No chance to get OpenVPN connections working?
Can you connect to your IPv6 address? It shouldn't matter to OpenVPN whether you connect via IPv4 or IPv6. It can also carry both.
but with this IPV4 & IPV6 stuff I am completely out of my depth
Other than address length, the fundamentals are much the same, though IPv6 relies on ICMP for a lot of things, such as Neighbour Discovery, instead of ARP on IPv4. There are a lot of referrences around that cover IPv6.
The smallest address block (/64) you get from an ISP contains 18.4 billion, billion addresses, but many ISPs provide a /56 or /48 prefix for 256 or 65536 /64s.
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Honestly I do not know if/how to connect with the IPV6 address as I never used it.
I made a quick hacky attempt to try it out - I got the WAN IPV6 address using ifconfig as a shell command, then replaced the OpenVPN host name in the client export with this address but no packets are received in the packet capture on 1194. It is late here and I am tired so possibly I overlooked something but so far no joy.
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The easiest way is to connect to ipv6.google.com, which is reachable via IPv6 only. You can also try a test site, such as ipv6-test.com or test-ipv6.com. These will show if you have IPv6 available at the remote site you're trying to connect from. If you have IPv6 available, using it is transparent, compared to IPv4. You really shouldn't notice any difference. Once you have verified you have IPv6 at both ends, just recreate the OpenVPN client with the IPv6 address. If possible, you can preferrably use the host name.
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Sitck with the ip (v6)address initially. Host name resolution for dynamically allocated ipv6 subnets is very rare.
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OK - this seems to be a good line of attack. From a first quick test I cannot access any of those IPv6 sites so I imagine there is something wrong with my PFSense - firewall rule, NAT or something else - that is missing.
From a first inspection of the firewall settings I do not see anything obvious and my setup is really simple, essentially a basic installation with nothing added. Any tips where to start? I will of course start Googling :)
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@charry2014 wan settings, ipv6?
Also system advanced networking allow ipv6 -
Many thanks - I now have IPv6 connecting. I found some helpful posts around the net (mostly in German as this is a German internet provider) - listed here for anyone who follows me:
beechy.de
glasfaserforum.de
And here gives some hints about things to look at for IPv6 - pfstore.com.auA combination of these things has made my IPv6 connect - The final detail was this
• 6rd Prefix: 2A00:61E0::
• 6rd Prefix Length: 32
• 6rd BR IPv4 Address: 100.127.0.1
• IPv4 Mask Length: 8Now to go back to OpenVPN and see if I can get that going.
Edit - still nothing. I reconfigured the VPN from scratch, following the wizard again. Got my IPv6 address from the sites mentioned above, used that directly in the client export. I get no packets logged on 1194.
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@charry2014 Only a reflector site will tell you your ip.
Status interfaces should have it
can you ping ipv6.google.com from pfsense cli? -
The WAN address may often have a host name which can be used. Use host or nslookup command on the WAN address to see what turns up.
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@charry2014 said in OpenVPN and Deutsche Glasfaser - IPV6 and CGNAT blocking connection?:
6rd Prefix: 2A00:61E0::
They're using a tunnel, rather than native IPv6. I used a tunnel for the first 6 years I had IPv6, but now I get a native IPv6 connection from my ISP. I'm surprised they're using a tunnel and CGNAT. How old is that info? My ISP also used a tunnel (though not the one I used) prior to providing native IPv6. If they're using a tunnel these days, I'd have to question their competence.
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Does your (smartphone) service provider has IPv6? Than you can connect OVPN via IPv6 directly.
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I could get my IPv6 address from https://ipv6-test.com/ easily enough but have drawn a blank trying to test OpenVPN connecting to it. Both running the OpenVPN client on my phone, and using the phone as wifi hotspot for my Mac result in no packets received at the PFSense WAN. Tunnelblick on Mac reports:
2020-07-26 15:43:16.288025 write UDPv6: No route to host (code=65) -
Please answer the question:
@Bob-Dig said in OpenVPN and Deutsche Glasfaser - IPV6 and CGNAT blocking connection?:
Does your (smartphone) service provider has IPv6?
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Yes. My phone (Samsung S20) is on Vodafone in Germany and I have read that they have IPv6 nationwide.
Edit - I did some digging and it has an IPv6 address too. -
@charry2014 That's great, you don't need any IPv4, at least not if you want to connect the phone to home via OVPN.
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The site https://ipv6-test.com/ reports that my firewall is filtering ICMP v6 messages. Could this be a problem for OpenVPN? I am suspecting it might. How do I enable this?
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No. How is your IPv6 configured? I think your ISP is doing native IPv6.
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I think so too, but I am not sure of much from my ISP.
One thing I did notice is that when I connect to whatismyipaddress.com or similar from different computers in my LAN that the IPv6 address that is returned is different for each one. The IPv4 address is the same, as I would expect. Now I think I am stumbling into a noob difference between IPv4 and IPv6 addresses.
So the question - what actually is the IPv6 address of my PFSense WAN?
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You can see it in the interfaces-gadget and other places.
(Status - Interfaces) -
Alright - so it is something like 2a00:61e0:abcd
:?It is not the much longer address 2a00:61e0:b00b5:34dd:6969:beef:babe:face?
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@charry2014 Can't say but maybe you did something wrong. Try this and go for DHCPv6 and not 6rd.
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Boom - that did it - using the IPv6 address for the WAN as shown in the Interfaces widget on the dashboard packets are now flowing.
I now get an authentication error, but the connection is there. Authentication errors are kinda the staple for getting OpenVPN working so somehow I am back on known territory now.
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No, OpenVPN uses UDP, not ICMPv6. However, ICMPv6 is used for a lot of things, so be careful about any rules blocking it.
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One nice thing about IPv6 is there are plenty of addresses to go around. This means no longer having to share an address with NAT. Not only does each device get an address, it will often get several. With SLAAC, privacy addresses are often used. These are random number based addresses and you get a new one every day. They expire after a week. This is in addition to the consistent address, so you could have as many as 8 public addresses on each device.
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Thanks everyone for your help - it seems that a little background reading would be a good idea sometime soon. This may well change the settings in the firewall rules, then?
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That depends on what the rules do. If filtering on protocol, then you can often create a single rule that handles both. If filtering on address, then you'd need separate rules.
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So here it is, best I can remember it. All the things I changed to get this working:
System - Advanced - Networking
Interfaces - WAN
Interfaces - LAN:
The PFSense WAN IPv6 address is then in the Dashboard.
Finally I meant to link to beechy.de above but got the wrong link pasted in.
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That link @Bob-Dig provided says 6rd is going to be shut down, which means you should be configuring for DHCPv6 instead. My ISP did the same thing. They provided both 6rd and 6to4 tunnels, until they provided native IPv6 via DHCPv6-PD. This is what you should be configuring for, as that link describes.
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@Bob-Dig said in OpenVPN and Deutsche Glasfaser - IPV6 and CGNAT blocking connection?:
this
Feeling brave I tried DHCPv6 like suggested instead of 6rd and from a quick late-night hack it broke the IPv6 connectivity for me. This is one for more experimentation.
For the moment my pressing requirement is to fix my OpenVPN authentication issue rather than future-proofing the IPv6 connection.
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My authentication problems seem to be documented as a PFSense bug here so I have downgraded the login to SSL/TLS only and it works. Will keep researching the correct settings for DHCPv6. Cue small celebration here...
One further question - is there any way I can access my home network over IPv4? This would be very handy, for one thing my employer only allows IPv4 traffic through their network, and I am sure to travel to corners of the world where the mobile network is not quite so modern as here. I have no idea what options there may be for this.
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If you mean connecting to your home network over an IPv4 tunnel, with IPv4 endpoints, probably not.
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Not with that CGNAT address. Perhaps you could get an IPv6 tunnel from he.net. It will send IPv6 in IPv4 UDP packets, similar to that 6rd tunnel you were using. Then you'd use IPv6 to access your network.
It sure will be nice when the world moves fully to IPv6, so that we can put all this NAT nonsense behind us.
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I think he was asking about accessing his network from an IPv4 source. Seems he has IPv6 worked out.
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Exactly that - I am able to reach my home network when the remote device is on an IPv6 capable network but I am willing to bet that much of the world is still IPv4 only. From these networks I apparently have no possibility to establish a link home, which seems a bit of a problem.
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That is why I suggested he.net. They will provide IPv6 over IPv4, so that you can access IPv6 from an IPv4 only network. I haven't used he.net myself, but I used to use a 6in4 tunnel from another provider. With it, I could arrange for a /56 for a network a single IPv6 address for a device. I'd get a single address for my notebook computer, in addition to the /56 for my home network. I used a 6in4 tunnel for almost 6 years. Your ISP provided a 6rd tunnel, but I doubt it could be used off their network.
