how to drop tcp ack and sync in pppoe-client

RouterOS General
1

Hi, i newbie in mikrotik.
i using pppoe client to connect my ISP.
the question is, how to drop tcp sync flag for specific or unused tcp port. so the server no need to reply tcp ack/sync flag.
seem, the server still reply tcp ack/sync flag even we drop the connection.

firewall filter to drop tcp port 8000:
add chain=input protocol=tcp dst-port=8000 in-interface=pppoe-out1 action=drop disabled=no

firewall filter to drop not dst-nat:
add chain=input protocol=tcp in-interface=pppoe-out1 connection-nat-state=!dstnat tcp-flags=syn action=drop disabled=no

the both filter is work, but the server still reply the client with tcp ack/sync.

  1. client send tcp ack to server << drop this packet, so the server no need to going to the step 2.
  2. server reply tcp ack and sync to client
  3. client send tcp ack to server
  4. client connected

router OS: 6.38.1 on RB450G