Packet Capture shows: Packet dropped - Connection Cache Add Failed
12/20/2019 176 People found this article helpful 404,236 Views
Description
Running a packet capture is showing a dropped packet as below:
Drop Code: Connection Cache Add Failed (or any type of Cache drop packet)
Cause
This can happen when one side of a TCP connection either ends (FIN) the connection or resets it (RST).The SonicWall keeps track of the state of the TCP connection and once it sees either of these two packets, it closes the socket.All subsequent packets sent on the same socket will be dropped because they are invalid (they reference a connection that no longer exists).
Resolution
In a Site to Site VPN context, to avoid these types of dropped packets it's strongly recommended to use Public IP addresses on the WAN interfaces of both sides of the VPN.
Indeed a double NAT in some network environments can cause issues with the packet transmission and as a consequence drops packets.
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