Sophos Connect blocks SNMP

Hello Michal,

Without additional information it is hard to pinpoint the exact cause of the problem you are having with Sophos Connect Client. What is the policy configuration? It is a tunnel all policy or a split tunnel policy? If it is a split tunnel policy check if the destination network includes the network where the server is located. There is nothing in Sophos Connect that will specifically block communication via UDP/161. 

Please let me know

Ramesh

Thank you for your response. This is tunnel policy with full access to all private addresses behind the router.

{
"name": "IT",
"managed": false,
"version": 1,
"gateway": "a.b.c.d",
"vip": "0.0.0.0",
"auto_connect": {
"name": "10.77.77.254",
"required": false,
"enabled": true
},
"proposals": "aes256-sha2_256-modp1024",
"dpd_delay": 60,
"rekey_time": 15300,
"start_action": "none",
"local_auth": {
"psk": {
"id": "0.0.0.0"
},
"xauth": {
"can_save": true
},
"otp": false
},
"remote_auth": {
"psk": {
"id": "%any",
"secret": "efgh"
},
"otp": false
},
"child": {
"rekey_time": 3060,
"remote_ts": [
"10.0.0.0/8",
"172.16.0.0/12",
"192.168.0.0/17",
"52.5.76.173/32"
]
}
}

However, it looks like the problem lies somewhere else. After establishing VPN tunnel through Sophos Connect, I get unexpectedly such a gate: 169.254.128.128.

IPv4 Route Table
===========================================================================
Active Routes:
Network Destination Netmask Gateway Interface Metric
0.0.0.0 0.0.0.0 192.168.178.1 192.168.178.222 25
10.0.0.0 255.0.0.0 169.254.128.128 10.0.101.200 45
10.0.101.200 255.255.255.255 On-link 10.0.101.200 291
52.5.76.173 255.255.255.255 169.254.128.128 10.0.101.200 45
127.0.0.0 255.0.0.0 On-link 127.0.0.1 331
127.0.0.1 255.255.255.255 On-link 127.0.0.1 331
127.255.255.255 255.255.255.255 On-link 127.0.0.1 331
172.16.0.0 255.240.0.0 169.254.128.128 10.0.101.200 45
192.168.0.0 255.255.128.0 169.254.128.128 10.0.101.200 45
192.168.137.0 255.255.255.0 On-link 192.168.137.1 311
192.168.137.1 255.255.255.255 On-link 192.168.137.1 311
192.168.137.255 255.255.255.255 On-link 192.168.137.1 311
192.168.178.0 255.255.255.0 On-link 192.168.178.222 281
192.168.178.222 255.255.255.255 On-link 192.168.178.222 281
192.168.178.255 255.255.255.255 On-link 192.168.178.222 281
224.0.0.0 240.0.0.0 On-link 127.0.0.1 331
224.0.0.0 240.0.0.0 On-link 192.168.178.222 281
224.0.0.0 240.0.0.0 On-link 192.168.137.1 311
224.0.0.0 240.0.0.0 On-link 10.0.101.200 291
255.255.255.255 255.255.255.255 On-link 127.0.0.1 331
255.255.255.255 255.255.255.255 On-link 192.168.178.222 281
255.255.255.255 255.255.255.255 On-link 192.168.137.1 311
255.255.255.255 255.255.255.255 On-link 10.0.101.200 291
===========================================================================

Meanwhile, all interfaces on the router have either a fixed IP address or are disabled. I do not have any virtual interfaces or bridges configured. So from where did the VPN server pick up such address? From which router interface?

Hello Michal,

That IP address is the WAN IP address of the gateway you are connecting to. You will find the defined gateway from this attribute "gateway": in the policy. Please let me know if you have any questions on this. 

Ramesh

Hello Michal,

It is possible you have a very restrictive firewall rule that could be blocking traffic to UDP/161. Please check the logs on the firewall and/or capture packets on the firewall destined for the SNMP server. That will help to narrow down the problem you are having.

Ramesh

Thank you again. We have two WAN gates, the main and the reserve one. Both have a fixed IP address.

Before asking questions on the group, I checked the firewall's settings and logs several times and all the snmp traffic is passed both ways. The problem is the strange gate that appeared on the client. In the case of normal SSL connection, the gateway address is the VPN server address on the router, that's why the communication works. But in the case of Sophos Connect the gateway is the address going nowhere and the packets do not return to the router anymore.
I would like to determine where this address comes from. Is it possible to look through ssh in the configuration files of the Sophos Connect server on the router?

You wrote: "You will find the defined gateway from this attribute "gateway": in the policy"

The gateway address in policy is exactly same as the address of our main WAN gateway. In the configuration I have pasted, I replaced it with a.b.c.d.

Michal,

The address you have specified  169.254.128.128 is not a routable address. So the first question is when you enable the connection in Sophos Connect, is the connection getting established? Based on the route table you have attached to the post it does look like it is established. Can you then do a ping test and confirm you are able to get bidirectional traffic going thru the tunnel. But then the IP  as seen in the route table is non-routable. So something is missing here which I cannot figure out without additional details. Let me know the answers to above and then we can go to the next step

Ramesh

Hello Michal,

There is one other thing that I think is the problem is due to. Probably in your case you are not getting a Virtual IP and as a result a non-routable IP address is getting assigned to the remote networks. That is the problem. If you open the Open VPN logs, you can search the logs for Virtual and see if there are errors there. 

Ramesh

Yes, the tunnel is set up correctly and I am getting correct IP address 10.0.101.200. This address is from the 10.0.101.0/24 subnet configured in the Sophos Connect settings on the router.

Yes, I can communicate with LAN addresses behind the router:
c: \> pathping -n 10.77.77.254
Tracing route is 10.77.77.254 over a maximum of 30 hops
   0 10.0.101.200
   1 10.0.101.100
   2 10.77.77.254
Computing statistics for 50 seconds ...
? C

The router sees the remote host on the tun0 interface and can ping it. However, for devices that are in the LAN behind the router, the host is unavailable.

I know that this is a non-routable APIPA address, but communication with the router and other devices behind it works.
On the screens I hav pasted you can see all the addresses both on the router and on the remote host. Below I will also add the routing table copied from the router.

Hello Michal,

Can you please check the firewall rule and check if traffic is allowed from VPN to LAN and then you can do a packet capture on the firewall to see if the firewall is dropping or allowing this packet on the LAN.

Ramesh

I have created the very first rule "allow all to 10.0.101.0/24 subnet":

Summary
sc
Allow
Rule
Accept any service going to "VPN" zone, when in any zone, and coming from any network, then apply log connections

Source & schedule
Any
Source networks and devices : Any
During scheduled time : All the time

Destination & services
VPN
Destination networks : VLAN 101 ssl vpn
Services : Any

Advanced
Synchronized security
Source : Minimum heartbeat is No restriction, Clients with no heartbeat allowed
Destination : Minimum heartbeat is No restriction, Request to destination with no heartbeat allowed

Masquerading is OFF

1. This is a packet capture screen with ICMP test from machine 10.77.77.8 behind the router to remote host 10.0.101.200:

First packet:

Second packet:

2. Another test - ping address 10.0.101.200 directly from the router:

First packet:

Second packet:

I have created the very first rule "allow all to 10.0.101.0/24 subnet":

Summary
sc
Allow
Rule
Accept any service going to "VPN" zone, when in any zone, and coming from any network, then apply log connections

Source & schedule
Any
Source networks and devices : Any
During scheduled time : All the time

Destination & services
VPN
Destination networks : VLAN 101 ssl vpn
Services : Any

Advanced
Synchronized security
Source : Minimum heartbeat is No restriction, Clients with no heartbeat allowed
Destination : Minimum heartbeat is No restriction, Request to destination with no heartbeat allowed

Masquerading is OFF

1. This is a packet capture screen with ICMP test from machine 10.77.77.8 behind the router to remote host 10.0.101.200:

First packet:

Second packet:

2. Another test - ping address 10.0.101.200 directly from the router:

First packet:

Second packet:

Maybe a more interesting test will be the other way around, from the remote host 10.0.101.200 to devices in the LAN behind the router.

Hello Michal,

I setup a VPN tunnel from my Sophos Connect Client to XG. I start a PING from my Sophos Connect Client (Virtual IP: 10.0.3.77) to a LAN host 10.1.1.11. I setup a packet capture with a host 10.0.3.77

You should see 4 packets as you seen in my capture. Incoming IPsec packet from 10.0.3.77 to 10.1.1.11. This packet is now forwarded on Port A to destination host 10.1.1.11. The host response is received on Port A, which is then forwarded to 10.0.3.77 on the VPN tunnel.

In your capture I only see the received packet from the IPsec tunnel that is forwarded out. There is nothing coming back. So please check the default route on the host to make sure the packet is correctly forwarded back to the XG firewall.

Please let me know.

Ramesh

Hi Ramesh,

I do not know what else to show, all information is on already available print screens. It is clear to me that in my case the packets sent to the remote host have status "Unreplied", while your packets are sent and correctly returned. This is probably because your Sophos Connect client sets the correct gateway - and my client does not.

The firewall on our router does not block any packets sent / received to/from the remote host. I apologize to you very much, but this discussion leads nowhere.

Do you have any suggestion why my Sophos Connect client gives the gateway an APIPA address for packets returning from the host? Do you know how I can check the settings (or logs) of the Sophos Connect server in the files saved on the router? Thank you.

Hey MichalKawecki 

Thanks for your continued patience and participation during your troubleshooting with rmk_2018 

I'd like to continue this investigation and troubleshooting with you. I'll reach out to you further via PM.

Regards,

This problem is now resolved. The problem was because the DHCP Range assigned to Sophos Connect and SSL VPN was in the same segment. Once that was separated out Sophos Connect worked as expected. 

The problem has been solved, for which I thank you very much. Nevertheless, I have a suggestion to enter a visual warning or even blocking the setting of the same network in Sophos Connect as in SSL VPN in the router settings.

Thank you again and have a nice day.

Hi Ramesh,

I have one more question. The router continues to allocate a non-routable gateway 169.254.128.128 to the remote host. Is this correct behavior of the Sophos Connect server?

IPv4 Route Table
================================================== =========================
Active Routes:
Network Destination Netmask Gateway Interface Metric
0.0.0.0 0.0.0.0 192.168.178.1 192.168.178.100 281
10.0.0.0 255.0.0.0 169.254.128.128 10.0.102.200 45
10.0.102.200 255.255.255.255 On-link 10.0.102.200 291
52.5.76.173 255.255.255.255 169.254.128.128 10.0.102.200 45

Hello Michal,

Yes that is correct. 

Ramesh

Thanks.