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Default Open Ports - 21-23-53-110

We have a Cisco Router 2811.

After doing a port scan, we found that ports 21, 23, 53, and 110 are open.

I can understand port 23 for remote telnet access but I'm confused about the rest.

I know for sure these ports are not open on our firewall. I have triple checked this.

Why is FTP (21), DNS (53) and POP3 (110 open by default? Can someone please explain? Any docs on how to close these would be helpful too.

Thanks in advance everyone.

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Re: Default Open Ports - 21-23-53-110

have you try a diffent port scanner?

i found couple port scanners will report those ports open regardless. i even tried to scan an ip that doesn't exist and still, the port scanner reports that those ports open.

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