Sophos UTM - IPv4/IPv6 Issue - IPSec

Hallo and welcome to the UTM Community!

I'm not familiar with the Mikrotik - can it do IPv6-to-IPv4?  Do you have UTMs in the branches, or are these other brands?

Cheers - Bob

Hi Bob!

Thanks for the reply - almost lost hope :)

Sorry, should have been more clear on that:

Main office: SG135 UTM

Branch1: SG125 UTM

Branch2: SG115 UTM

The Mikrotik antenna has the so called "routerOS", but I activated the passthrough mode (similar to the bridge mode on a router), so the Mikrotik only uses the built-in LTE modem to forward the public IP - this has been tested and confirmed by me.

Thanks and best regards

Constantin

Did you check the firewall log, Constantin, to see if pings are blocked there?  If they are, see #2 in Rulz (last updated 2019-04-17).

Cheers - Bob

Hey Bob,

I observed on both sides the Live Log of the firewall and there are no drops of any kind when I try to ping (I also turned off IPS and ATP), only timout:

Not sure what else we could do. Can we listen "inside" the tunnel with tcpdump? So we know that the ping at least went into the tunnel?

Thanks and best regards,

Constantin

First, we need the REF_ of the tunnel.  If "Branch 1" is the name of the IPsec Connection, which we can find with:

cc get_object_by_name ipsec_connection site_to_site 'Branch 1'|grep \'ref

That will return something like REF_IpsSitBranch1.

To watch the traffic in the tunnel:

espdump -n --conn REF_IpsSitBranch1 -vv

Cheers - Bob

Hey Bob,

now Im really confused. The ping clearly goes into the tunnel and is even noticed on the other side.

Branch1:

HQ:

Not sure what else to do here. I checked all the logs - firewall, IPS, ATP - in the end I turned off intrusion prevenion and atp but that didnt help in any way.

Do you have another approach?

Thanks and best regards,

Constantin

I read right past the key log line last week, Constantin.  The error occurs immediately after initiate Main Mode.

That tells me that the IP address on LTE_Backup is not the same as the one on the public interface of the Mikrotik.

Try the following:

1. In both branches, change the 'VPN ID type' to "IP address" and leave the 'VPN ID (optional)' empty.
2. In the HQ, change the 'VPN ID type' to "IP address" and set the 'VPN ID (optional)' to the IP on the LTE_Backup interface.

Any better luck with that?

Cheers - Bob

Hey Bob,

sorry for the delay. The guy in the branch office went on holiday and turned his computer off. Phantastic. Drove there last night and turned it on again. Anyway, I was under the impression that the Mikrotik antenna would just "forward" the received public IP address when in passthrough mode.

When I try to set the IP in the HQ I get the following message:

Thanks and best regards,

Constantin

Probably not related, but wanted to update the running configuration so we are all on the same page at all times.

It bugged me, that I couldnt get the tunnel with RSA running, so I played around with the settings. When I changed this setting to IP Address instead of hostname:

and here to:

 The tunnel was finally established:

I know its not relevant, but I wanted to keep the thread up2date.

Best regards,

Constantin

Hey Bob,

just to definitely rule out firewall drops, I logged the automatic rule for the IPSec tunnel, but alas no luck, i.e. no ICMP drops in the log. I looked at another protocol and tried nslookup for a change:

09:48:15.514701 IP6 (hlim 64, next-header ESP (50) payload length: 104) 2003:a:XXXXXXXXXXXXXXXXX > 2a01:598:XXXXXXXXXXXXXXX: ESP(spi=0xc73de4ae,seq=0x5), length 104: IP (tos 0x0, ttl 127, id 51386, offset 0, flags [none], proto UDP (17), length 68)
10.2.1.15.60868 > 10.1.4.13.53: [udp sum ok] 1+ PTR? 13.4.1.10.in-addr.arpa. (40)

I checked the firewall logs at branch office and I saw:

This is just bizarre. Any other ideas?

Thanks and best regards,

Constantin

Well, Constantin, if the packet capture shows the request packet going through the tunnel, but doesn't show the response packet returning through the tunnel, the only thing left is the firewall settings on the device you're trying to ping - ni't?

Cheers - Bob

Hi Bob,

sure, but the exact same pinging action works through the usual IPv4 IPSec tunnel, which was also created with automatic firewall rules and routing. 

Phew, I have no idea what else I could do... I guess that means the project failed.

Thanks anyway for your time and effort!

Best regards,

Constantin

Hi Bob,

sure, but the exact same pinging action works through the usual IPv4 IPSec tunnel, which was also created with automatic firewall rules and routing. 

Phew, I have no idea what else I could do... I guess that means the project failed.

Thanks anyway for your time and effort!

Best regards,

Constantin

@ Constantin

Sorry to hear about your problem. Hope that I can help looking into a bit if it is not too late

Hello Duc,

thanks for the reply - I would be grateful for any further suggestions how I can tackle this. The "damage is done" you might say (about 177 bucks for that Mikrotik antenna - of course it could be put to other use), but it still bugs me that it would not work, even though it should!

Thanks and best regards,

Constantin

Hi Constantin,

You are right, it should work.

Sure I can give a good try (quite busy at the moment); but no guarantee that I will find anything useful.

Anyway, Can we take this conversation private?

Thx