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We have several servers they have public IP's, but work together (one is with Load Balancer, orther with Apache Web server, other with MySQL and so on.

Most of the ports are fire-walled, so only "local" servers can be connect there. However ALL servers have some ports that must be publicly open.

We have SYN Cookies enabled and from time to time we got:

possible SYN flooding on port 8080. Sending cookies.

Port 8080 is not public. How we can switch OFF SYN Cookies for some ports (e.g. 8080, 3306 etc) or from some sources (e.g. our servers),

but in same time SYN Cookies to be switched ON for all other ports, e.g. port 80.

We found this similar problem, except our servers are with public IP's: SYN cookies on internal machines

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What's your outer problem? Why do you want to switch off SYN cookies for some ports? –  David Schwartz Oct 12 '12 at 9:29
    
Because those ports are fire-walled an are accessing only from trusted machines. When we have SYN cookie, the service there is unresponsive. –  Nick Oct 12 '12 at 12:40
    
I got that. But why do you want to switch off SYN cookies? Are they causing you a problem? (That's an argument that you don't need them on. It's not an argument that they should be off.) –  David Schwartz Oct 12 '12 at 12:41
    
from time to time server is not responding. we can login via second LAN adapter, and we can see in dmesg lots of messages like: possible SYN flooding on port 8080. Sending cookies. –  Nick Oct 12 '12 at 13:03
    
What do you want to happen when the number of incoming connections is more than the application can accept concurrently? –  David Schwartz Oct 12 '12 at 13:11

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