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Sophos XG - Connection being dropped in IPSec tunnel

Hey there,

we're currently facing a serious issue with a brand new XGS116 (SFOS 18.5.3 MR-3-Build408) and already contacted Sophos support about this, but unfortunately they don't seem to be able to help us.

We switched one of our customer's UTM with a XGS116 a few weeks ago. Anyway, we set up an IPSec tunnel to another hosting company, who is hosting their SAP Database. Same setup as before. Tunnel is stable and it basically never disconnects. 

But here's the issue. At some point, and this happens multiple times every day, the SAP program freezes and packages are being dropped by the firewall. Application filter, Webfilter etc. is not even licensed and we already turned off IPS and everything else that might cause this (plus, the Sophos support double checked this too).

What we're seeing in the logs of the firewall the moment it happens is this:

 

messageid="01001" log_type="Firewall" log_component="Invalid Traffic" log_subtype="Denied" status="Deny" con_duration="0" fw_rule_id="N/A" nat_rule_id="0" policy_type="0" user="" user_group="" web_policy_id="0" ips_policy_id="0" appfilter_policy_id="0" app_name="" app_risk="0" app_technology="" app_category="" vlan_id="" ether_type="IPv4 (0x0800)" bridge_name="" bridge_display_name="" in_interface="xfrm2" in_display_interface="xfrm2" out_interface="" out_display_interface="" src_mac="" dst_mac="" src_ip="10.213.42.11" src_country="R1" dst_ip="192.168.105.161" dst_country="R1" protocol="TCP" src_port="3200" dst_port="57133" packets_sent="0" packets_received="0" bytes_sent="0" bytes_received="0" src_trans_ip="" src_trans_port="0" dst_trans_ip="" dst_trans_port="0" src_zone_type="" src_zone="" dst_zone_type="" dst_zone="" con_direction="" con_id="" virt_con_id="" hb_status="No Heartbeat" message="Invalid packet." appresolvedby="Signature" app_is_cloud="0"

 

messageid="01001" log_type="Firewall" log_component="Invalid Traffic" log_subtype="Denied" status="Deny" con_duration="0" fw_rule_id="1" nat_rule_id="0" policy_type="1" user="" user_group="" web_policy_id="0" ips_policy_id="0" appfilter_policy_id="0" app_name="" app_risk="0" app_technology="" app_category="" vlan_id="" ether_type="IPv4 (0x0800)" bridge_name="" bridge_display_name="" in_interface="" in_display_interface="" out_interface="" out_display_interface="" src_mac="" dst_mac="" src_ip="10.213.42.11" src_country="R1" dst_ip="192.168.105.161" dst_country="R1" protocol="TCP" src_port="3200" dst_port="57133" packets_sent="0" packets_received="0" bytes_sent="0" bytes_received="0" src_trans_ip="" src_trans_port="0" dst_trans_ip="" dst_trans_port="0" src_zone_type="" src_zone="" dst_zone_type="" dst_zone="" con_direction="" con_id="" virt_con_id="" hb_status="No Heartbeat" message="Invalid TCP state." appresolvedby="Signature" app_is_cloud="0"

We also checked the log on the other site of the tunnel and it says the client closed the connection.

What we tried so far:

 

  • Re-created the tunnel on both sites
  • Switched from a site-to-site tunnel to a route-based tunnel
  • Re-created the rules
  • Deleted/Added new rules (LAN-VPN, also WITH the Sophos support)
  • Setup a bypass rule, which caused the tunnel to not work anymore.

 

The local subnet is 192.168.105.0/24 and the subnet on the other site of the tunnel is 10.213.42.0/24. Remote access works fine too.

Here's a screenshot of the firewall rule:

 

We really do not wanna do a factory reset cause we already setup 2FA with every employee, but we're completely lost here. It doesn't make any sense and we haven't heard back from Sophos support in over a week.

Could this be a firmware or even hardware issue? Any help is much appreciated! Thank you!



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  • Hi,  Thank you for your detailed information. Very less chances of hardware issues. To confirm it is something on the firmware side or any other issue due to packet loss or delayed communication you may check the PCAP on 3400 on XG, drop, Conntrack, and TCPDUMP on the same port number. Also, PCAP (by installing Wireshark) on the end machine and on the SAP server will be more helpful to conclude things in a better way. By comparing all these details you may confirm on which side packets are having some trouble due to which it is creating a frozen state on the end Application. 

    Regarding TCP Invalidate state or Invalid packet may have multiple reasons and a few of them is delayed reply or re-transmitted packet.

    Regards,

    Vishal Ranpariya
    Technical Account Manager | Sophos Technical Support

    Sophos Support Videos | Knowledge Base  |  @SophosSupport | Sign up for SMS Alerts |
    If a post solves your question use the 'This helped me' link.

  • Greetings!  I am almost CERTAIN this is a firmware issue.  I have 2 x Sophos XG 116 (one on firmware SFOS 19.0.0 GA-Build317, and the other on SFOS 18.5.1 MR-1-Build326).  Both of these devices have identical VPN site to site IPSec tunnels with the same provider (same endpoint firewall on provider's end as well), and the only one having issues is the unit that has the 19.0.0 firmware.  The IpSec tunnel stays active, but as described in this post the logs show "invalid traffic" and starts dropping packets at random intervals.  

  • I can confirm that after rolling back to SFOS 18.5.0 the issue has gone away.  The problem being all of my backups were on the newer firmware, so I had to reconfigure EVERYTHING from scratch.  I saw on another post something about disabling IPSEC acceleration as a workaround, but I didn't test that before going back to the previous firmware.  Hope this helps someone. 

  • Try turning off the firewall acceleration 

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  • Hi LuCar.  Thank you for the reply.  Where is that setting at?  I am using Firmware version 18.5.0 now

  • You can disable it on the Firewall CLI: docs.sophos.com/.../index.html

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  • please post the IPSec policy of the XGS used for that S2S. What is on the remote side of the tunnel at the hosing provider?

    Try to enable the compression on your XGS IPSec policy. This helped us in a similar situation.

  • Thanks.  I did this but I'm STILL seeing Dropped packets due to "invalid packet".  This is still occurring on firmware 18.5.0, but causing less disconnects. Shouldn't be dropping any of them at all as I have all services set to allow on the VPN tunnel and associated firewall rule (automatically created during S2S IPSEC VPN  configuration)

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  • Thanks.  I did this but I'm STILL seeing Dropped packets due to "invalid packet".  This is still occurring on firmware 18.5.0, but causing less disconnects. Shouldn't be dropping any of them at all as I have all services set to allow on the VPN tunnel and associated firewall rule (automatically created during S2S IPSEC VPN  configuration)

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