Important note about SSL VPN compatibility for 20.0 MR1 with EoL SFOS versions and UTM9 OS. Learn more in the release notes.

Sophos Firewall: v20.0 MR1: Feedback and experiences

Release Post:  Sophos Firewall OS v20 MR1 is Now Available 

The old V20.0 GA Post:  Sophos Firewall: v20.0 GA: Feedback and experiences  

To make the tracking of issues / feedback easier: Please post a potential Sophos Support Case ID within your initial post, so we can track your feedback/issue. 

Release Notes:  https://docs.sophos.com/releasenotes/output/en-us/nsg/sf_200_rn.html 

Important Note on EOL Sophos RED Support:

The legacy EOL RED 15, RED 15w, and RED 50 are not supported in v20 MR1. Customers using these devices should upgrade to SD-RED or a smaller XGS appliance before upgrading to MR1 to maintain connectivity. See the following article for details: Sophos RED: End-of-life of RED 15/15(w) and RED 50



Prio Change
[bearbeitet von: LuCar Toni um 4:40 PM (GMT -7) am 23 Sep 2024]
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  • Hi,

    since the update to SFOS 20-MR1, we have had an interesting problem on one firewall (this does not occur on the other approx. 90 firewalls)

    The firewall has 2 Internet uplinks that run to a router from the provider, the router assigns a public IP address via DHCP, up to and including version SFOS 20 we had no problem. After the update was installed, the firewall was difficult to reach from the Internet. For a few seconds the firewall was reachable, then again for a few seconds the firewall was not reachable. This alternated continuously. Restarting the firewall did not change anything.

    A rollback to the old version (SFOS 20) restored a stable state. I then contacted the provider. The DHCP lease is renewed every 40 seconds on both WAN connections. The provider gave me the option of using static IPs on the two WAN connections. 

    So I activated the update to MR-1 again and observed the described unstable behavior with the DHCP on the two WAN connections. It only became stable when I configured one of the two WAN ports with a static IP. At the moment it is very stable with a static WAN connection and a WAN via DHCP (lease time 40 seconds):

    I suspect that the behavior can be explained by this change in the MR-1:

    Sophos release notes  

    "DHCP lease time: DHCP clients will make renewal requests at 30 seconds if the lease interval's half-time is 30 seconds or less, ensuring continuous WAN connectivity."

    BR,

    Ben

    If a post solves your question please use the 'Verify Answer' button.

  • Hi Ben,

    Thank you for sharing feedback.

    Please help to share the below information to troubleshoot the issue.

    1. Is all 90 firewalls are on v20.MR1 and they have DHCP WAN with 40 sec lease time from the provider?

    2. Just for curiosity to understand the field deployments better, is 40 sec lease time common with your provider? Any specific reason for such lower lease time?

    3. Please share the support access via PM.

  • Hi Jekin,

    thanks for the quick response

    >> 1. Is all 90 firewalls are on v20.MR1 and they have DHCP WAN with 40 sec lease time from the provider?

    All 90 firewalls are now running on 20-MR1. On two firewalls we have connected the ISP with the 40 sec. DHCP. One of the firewalls has the "dual" 40 sec. DHCP (where I posted the screenshots). The other firewall had a single 40 sec. DHCP. On this firewall we had some up and down events in the log (not as many as the first). 

    >> 2. Just for curiosity to understand the field deployments better, is 40 sec lease time common with your provider? Any specific reason for such lower lease time?

    The ISP says he has a lot of smaller customers who replace their firewall and get nervous if the new firewall doesn't get an IP address right away. These 40 seconds should have been compatible with all possible firewalls up to now. Sophos firewalls (up to and including SFOS 20) have also had no problems with this short lease time. 

    >> 3. Please share the support access via PM.

    I'll send you the Access IDs by PM shortly.

    Ben

    If a post solves your question please use the 'Verify Answer' button.

  • Hi Ben,

    Thank you for providing the support access. 
    We identify this behaviour is a side effect of improvement in the DHCP client in v20.MR1 release and tracking with NC-136619.
    With improvement in v20.MR1, the actual lease time will be used whereas in v20.GA the minimum lease time used was 120 seconds. 
    As per the DHCP client, the renew happens when dhclient script(executed on IP lease) execution takes less time compared to renew time(lease time/2).
    For your case, the dhclient script took more time than the renew time(20 seconds) hence the renew was not sent by the client the lease was lost and a fresh IP discovery was sent. 
    Due to this, the gateway and internet is flapping.
    This issue can be observed on earlier releases if dhclient script takes more time(depending on the processing power and no of DHCP interfaces and CPU usage) than the renew time but is aggravated with the changes with lower lease time.
    This is can be mitigated by increasing the lease time in the DHCP server by ISP.

  • Hi Jekin,
    thank you for the analysis. I will discuss this with our provider to see if it is possible to set the lease time to longer than 120 seconds. 
    Ben

    If a post solves your question please use the 'Verify Answer' button.

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