topic Re: ISE PSN nodes using telnet to communicate in Network Access Control

ISE PSN nodes using telnet to communicate

aravikumar — Fri, 03 May 2019 17:19:19 GMT

Hello All,

ISE PSN nodes are trying to communicate using telnet in our production environment. Does a PSN node communicate using telnet is it is enabled for SSH? Is there any scenario where a PSN nodes needs telnet to communicate?

Thanks,

Aravind.

Re: ISE PSN nodes using telnet to communicate

howon — Fri, 03 May 2019 17:52:26 GMT

ISE utilizes NMAP to port scan well known ports for the endpoints and also get banner text from telnet sessions to fingerprint OS for profiling.

Re: ISE PSN nodes using telnet to communicate

aravikumar — Fri, 03 May 2019 17:57:06 GMT

Thank you for your quick response. There are lots of telnet sessions from PSN nodes. According to your explanation, If NMAP probe is turned on for the PSN, all the port scans happen using telnet. right?

Thanks,

Aravind.

Re: ISE PSN nodes using telnet to communicate

howon — Fri, 03 May 2019 18:16:37 GMT

We use mostly default NMAP scan options which uses SYN scan among other operations. In terms of telnet, it doesn't finish the transaction, but grabs the banner text from the target OS to get hints on potential OS type.