Check Point – Upgrade Without Dropping Connections
Check Point firewall upgrades have always been painful. The loss of connection state is a big part of this. Existing connections stop working, and many applications need restart. It looks like there is a way of minimising this pain on upgrade.
Stateful firewalls record the current ‘state’ of traffic passing through, so they can recognise and allow reply or related traffic. If you have a firewall cluster, they need to synchronise state between the cluster members. This is so that if there is a failover, the new Active node will be aware of all connections currently in flight.
If you have a failover, and the standby member is NOT aware of current connection state, it will drop all currently open sessions. Any packet that isn’t a SYN packet will get dropped, and the applications need to establish new connections. Some applications handle this well – especially those that use many short-lived connections such as HTTP or DNS. But other applications that have long-running connections – e.g. DB connections – may struggle with this. They think the connection is still open, and take a long time to figure out it’s broken. They may eventually recover on their own, or they may Continue reading