Hello, On Mon, May 15, 2023 at 09:40:10AM +0800, Tom Reed wrote: > Yes after each telnet from client host, the count was increased. > > 0 0 REJECT tcp -- any any anywhere > anywhere tcp dpt:imaps reject-with tcp-reset > 0 0 REJECT tcp -- any any anywhere > anywhere tcp dpt:imap2 reject-with tcp-reset > 99 4620 REJECT tcp -- any any anywhere > anywhere tcp dpt:submission reject-with tcp-reset
In that case, we must conclude that the TCP RST being sent back never gets to your source host. You can try a tcpdump at both ends that shows only RST packets: # tcpdump -n -v "tcp[tcpflags] & (tcp-rst) != 0" then when you do the telnet, do you see a packet with "Flags [R…]" at both server side and client side? You could also try --reject-with icmp-port-unreachable to see if that behaves differently. Thanks, Andy -- https://bitfolk.com/ -- No-nonsense VPS hosting
