Sophos Firewall Route traffic through GRE Tunnel

Hello Raphael Alganes 

What's the route you have added for GRE, if its specific subnet then X4B.net might be expecting you to forward all traffic to them (i.e. default route need to be added)

With GRE, you can only add static routes and policy routing (specific service based routing - SMTP in your case) is not possible. alternatively you can opt for route based VPN and then create SD-WAN policy routes for your requirement.

Hi Hardik,

Thank you for getting back to me. The route that I added for GRE was 10.16.0.124/255.255.255.252. I did this with the following command: system gre route add net 10.16.0.124/255.255.255.252 tunnelname gre.

X4B.net supplied me with the following info for the tunnel:

I created the GRE tunnel with the following command:

system gre tunnel add name gre local-gw PortB remote-gw ***.**.***.** local-ip 10.16.0.126 remote-ip 10.16.0.125.

X4B.net also give a script to add the tunnel to a Windows / Linux environment, but doing this would (I think) stop me from being able to use the email protection feature on the Sophos Firewall, as everything would be done within the server hosting Exchange.

Regards,
Richard

Hello Richard,

According to this config, firewall will only forward traffic destined for 10.16.0.124/255.255.255.252 to GRE tunnel and other traffic will still pass through regular WAN gateway.

I assume you have followed the article from X4B.net related to mikrotik router in which they are adding the default route (0.0.0.0/0)

So you have 2 option:

1. Forward all traffic to GRE 
2. Opt for route based VPN and then create SD-WAN policy routes for your requirement to route specific SMTP traffic to X4B.since With GRE, you can only add static routes and policy routing (specific service based routing - SMTP in your case) is not possible.

Hi Hardik,

Thank you for getting back to me and with the suggestions, I really appreciate it. I am just trying to get my head around this but really struggling with the lack of support from X4B. They don't appear to want to help or answer my question if port 25 needs administrator approval or not from their end. I discovered one of their guides that stated that some ports below port 80, require approval at their end.

I think what is making this process most confusing is that I still have a Sophos UTM in the middle of this. I only have one WAN connection and that is connected to the Sophos UTM. I then have the Sophos Firewall running as a VM with the WAN port on the DMZ network. I have tried creating a DNAT rule on the Sophos UTM, to direct all GRE traffic from the WAN port, to the IP of the WAN port of the Sophos Firewall. I can see when I try to ping the tunnel from the X4B side, that the ping hits the WAN port of the Sophos UTM and then the DNAT rule moves it over to the Sophos Firewall. I can see this in the connection list on the Sophos Firewall as well, but the ping from the X4B end shows as failed. I think I need a NAT rule on the Sophos Firewall to route it back through to the Sophos UTM?

The Sophos Firewall is really confusing me a bit as Sophos UTM didn't have zones etc. and I am really struggling to get my head around this. It's also quite difficult not to have a live firewall log any more, I'll miss the live firewall log from the Sophos UTM... really useful when trying to diagnose something!

I really think I'm not going to be able to achieve what I am trying to achieve as I have zero support from the X4B side. I can currently ping the tunnel from the Sophos Firewall, but can't ping the tunnel from the X4B side. I tried option 2 from your list and I can see from the log that SMTP traffic is being sent to the GRE tunnel, but the email gets bounced and I don't see anything on the Sophos UTM firewall log (it's as if it isn't leaving the Sophos Firewall? / Doesn't know how to?) Also, when I add the route with 0.0.0.0/0.0.0.0, I can then no longer ping the tunnel from the Sophos Firewall. If I delete that route, the ping is then successful again.

I've nearly spent a month on this now trying to get this to work, I just wish there was a guide from start to finish on setting up a GRE tunnel through NAT and routing traffic through it on the Sophos Firewall.

Cheers,
Richard

Hi Hardik,

After doing more testing, it turns out that what I have currently set on the Sophos firewall is correct. As a test (now disabled), I added an Any>Any rule on the Sophos UTM firewall and the test email sent successfully over the GRE tunnel. I just now need to work out what rule I need to create on the Sophos UTM firewall to allow this to function! The strange thing is that when looking at the Sophos UTM firewall log whilst sending a test email, nothing in relation to the Sophos Firewall or the GRE tunnel show as being blocked.

Richard

Hello Richard,

Good to see the progress.

To identify what rule you need to create, you can check the Sophos UTM firewall log related to that test rule you have created and observer the source/destination IP/Port while sendinng test email and accordingly create specific rule.

Since this will mostly be GRE packets, I assume all traffic will have the destination IP within the 10.16.0.124/30.

Hi Hardik,

Thank you for your help again. I have created a rule on the Sophos UTM that will simply allow any source to go to and from the WAN IP of the Sophos Firewall. This has worked, maybe not the best approach but I plan on eliminating the Sophos UTM in a few months time if all goes well.

I am just trying to get incoming mail to work through the tunnel. I can see incoming mail reaching the Sophos Firewall, but nothing is showing in the Mail Spool / Logs. I think it is because the GRE tunnel interface doesn't have SMTP Relay enabled, I wondered if there was a SSH command to do this as the tunnel interface doesn't show in the GUI?

This is the log entry that's showing traffic for incoming SMTP from the tunnel:



Cheers,
Richard

Hi Hardik,

Thank you for your help again. I have created a rule on the Sophos UTM that will simply allow any source to go to and from the WAN IP of the Sophos Firewall. This has worked, maybe not the best approach but I plan on eliminating the Sophos UTM in a few months time if all goes well.

I am just trying to get incoming mail to work through the tunnel. I can see incoming mail reaching the Sophos Firewall, but nothing is showing in the Mail Spool / Logs. I think it is because the GRE tunnel interface doesn't have SMTP Relay enabled, I wondered if there was a SSH command to do this as the tunnel interface doesn't show in the GUI?

This is the log entry that's showing traffic for incoming SMTP from the tunnel:



Cheers,
Richard