8/16/2023 0 Comments Unreplied vs assured connection![]() You end up in a situation where the firewall consumes far more resources than the sever itself. Unfortunately as you have discovered this sucks for stateless UDP servers serving large numbers of small requests. But its that initial connect and waiting thats the issues. DNS is setup correctly, we have no issues on prem and once the VPN 'figures it out' everything works fine. There are no security implications other than DoS. But sometimes it doesnt at all and the answer is to reboot, connect to the VPN before doing anything else, waiting 1 - 2 minutes, and then trying to access the network resource. The entry tells us that the connection has not seen any traffic in both directions, will be replaced by the ASSURED flag, to be found close to the end of the entry. The message means your connection tracking table is full. ![]() ![]() In principle it would be possible to build a NAT box that used a stateless approach for port forwards while maintaining a stateful approach for outgoing connections but it's simpler to just use stateful NAT for everything and it sounds like this is what your vendor is doing. When a connection has seen traffic in both directions, the conntrack entry will erase the UNREPLIED flag, and then reset it. So it has to wait for a timeout before removing the entry from it's state tracking tables. Unfortunately the firewall or NAT has no way of knowing when the client has finished talking to the server. HTTPS is a protocol that, among other things, ensures that you are communicating with the server that you think you are. I would not be worried about half a dozen SYNs thats probably just part of normal operations. This allows rules like "outgoing connections only" to be applied to UDP and allows reverse translations to be applied to response packets. Any time you make a TCP connection (for instance, visiting a website), the connection process goes through SYN to SYN/ACK to ACK. Stateful firewalls and NATs therefore assume that packets with a given combination of source IP/source port/Destination IP/Destination port and the corresponding combination with source and destination swapped form part of a "connection". While there is no formal "connection" with UDP there is still a convention that clients send requests and expect to get responses back with the source IP and port swapped with the Destinatoin IP and port.
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