Cisco Support Community
cancel
Showing results for 
Search instead for 
Did you mean: 
Announcements

Welcome to Cisco Support Community. We would love to have your feedback.

For an introduction to the new site, click here. And see here for current known issues.

New Member

"transport input none"?

Hi,

What is the command "transport input none" for? The above is configured on Line con 0.

Thanks.

Said

1 ACCEPTED SOLUTION

Accepted Solutions

Re: "transport input none"?

By default cisco routers will allow telnet connections to TTY lines on TCP ports 2000 + the line number. For example the AUX port on a router is usually TTY 5, therefore if you telnet to the router but use destination TCP port 2005 you will connect to the router but the input will be directed to the AUX port. This gives you Terminal Server capabilities and is commonly used to connect to router/switch console ports via a router with a multiport async card (NM-32A etc).

I have seen some routers that don't allow inbound connection to the console port (transport input command isn't supported on the con 0 line), others it seems to work - probably an IOS thing...

Have a look on CCO for reverse telnet for more information.

HTH

Andy

8 REPLIES

Re: "transport input none"?

It disables access to console 0 as it prevents any protocol selection on the line. This makes the port unusable by incoming connections.

--Sundar

New Member

Re: "transport input none"?

Sundar,

Does "transport input none" not allow me to console in to the router and change configs...? If the above is true, the the only way to access the router is using telnet or aux port--am I correct?

Said

New Member

Re: "transport input none"?

Thanks.

Hall of Fame Super Silver

Re: "transport input none"?

I have seen transport input none configured on vty lines and the behavior is as Sundar describes that it prevents access to the vty lines. I was not sure that it works the same on the console (I believe there is a different behavior for tty than for vty). So I attempted to configure transport input none on a console port. I got an invalid command response. So I do not believe that this command works on console ports.

HTH

Rick

Re: "transport input none"?

When applied to the console or Aux ports it stops reverse-telnet connections to these ports, it won't stop you physically connecting a console and logging into the router. To prevent anyone getting access to the router CLI (the exec) on these ports you can turn off the exec process on these lines:

line aux 0

no exec

HTH

Andy

New Member

Re: "transport input none"?

Andrew,

Excuse my ignorance, but how do you reverse-telnet to a console port?

Thanks.

Said

Re: "transport input none"?

By default cisco routers will allow telnet connections to TTY lines on TCP ports 2000 + the line number. For example the AUX port on a router is usually TTY 5, therefore if you telnet to the router but use destination TCP port 2005 you will connect to the router but the input will be directed to the AUX port. This gives you Terminal Server capabilities and is commonly used to connect to router/switch console ports via a router with a multiport async card (NM-32A etc).

I have seen some routers that don't allow inbound connection to the console port (transport input command isn't supported on the con 0 line), others it seems to work - probably an IOS thing...

Have a look on CCO for reverse telnet for more information.

HTH

Andy

New Member

Re: "transport input none"?

Andrew,

Thanks.

Said

13908
Views
5
Helpful
8
Replies
CreatePlease login to create content