NAT is probably the most common one, at my company we run into strange issues because some idiot enabled tw_recycle. In our situation we used a hardware load b

NAT is probably the most common one, at my company we run into strange issues because some idiot enabled tw_recycle. In our situation we used a hardware load balancer (F5 Viprion) which worked in active-active mode. The tw_recycle was enabled on the server nodes that were load balanced. Long story short, everything worked fine until some traffic was applied, then some connections started to hang for few seconds. Our first assumption was that the load balancer had issues or the switches it was connected to. It took tons of hours and packet captures to realize that the problem was due to differences of tcp timestamp (blades don't have exact same time and per rfcs they don't need to) and then tracing dependence on timestamp to this setting. So please don't enable this setting, everything might work fine initially in your setup for months, then the one day you will observe strange behavior and start pulling your hair trying to figure out what's going on.