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why my external DMZ can always connect to Internet then i want not the DMZ has access to Internet and sub network(Informatique and Administration). What's wrong in my config.

  • I'm not certain I understand what you are trying to do. Can you explain it again? – Ron Trunk Jul 3 '16 at 21:37
  • Ok i have an external DMZ which connect to Internet and i want to deny this connection. I tried some ACL but it blocks all traffic instead the only i want. – google Jul 3 '16 at 22:22
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I'm going to try again, now that I think I understand your requirements better.
I think you want to allow inbound connections to the DMZ, but deny outbound connections from the DMZ

ip access-list extended Deny-Outbound
permit tcp any any established
permit icmp any any echo-reply

interface fa 0/0
ip access-group Deny-Outbound in

If this isn't what you want, please help me understand better.

| improve this answer | |
  • Thanks you very much it work. So i have a question about these 2 words established and echo-reply, they are keywords or just a name you take ? I'm not yet familiar with the ACL. – google Jul 4 '16 at 1:43
  • They are keywords. "Established" only permits tcp packets with the ACK flag set. A new connection doesn't have that flag set, so it will be blocked. "Echo-reply" only allows responses to pings (echo-request). So you can ping the DMZ, but the DMZ can't ping out. – Ron Trunk Jul 4 '16 at 1:47
  • I forget to ask you something about Radius Server, is it possible to block that server for some user of sub network ? I tried one like this but it doesn't work: access-list 101 deny udp 192.168.40.0 0.0.0.255 192.168.20.0 0.0.0.255 eq 1645 – google Jul 4 '16 at 2:04

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