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Community Member

Changing returned message from router when using ACL

Hi,

I configured a few voice routers that are directly exposed on Internet. They have access-lists that denies all the sip and h.323 traffic. When I'm scanning the router for example with nmap (syn scan) I get message that the port is open (administratively filtered). I just want to deny any responses on that ports like the and hide my router at all. Is there a way to do that?

Thank you in advance.

Regards,

Zdravkov

2 REPLIES
Gold

Re: Changing returned message from router when using ACL

you need to use the --packet-trace option of nmap to see what, if anything, is actually being returned by the router. By default, I believe Cisco routers will reply with a helpful ICMP message. You can filter outbound ICMP using an ACL. You may be able to selectively disable certain ICMP types via a more global setting too. Post this question to the firewall group with your router model and IOS version and you're sure to get a good response.

Community Member

Re: Changing returned message from router when using ACL

Thank you very much. If I don't find any better ideias I'm going to filter the outgoing icmps.

Regards

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