SSH Configuration Question

astrogeek

I'm reading up on SSH but I'm a little confused by how I've seen some switches configured. I have 2 questions:
1st question; These switches have both transport input ssh and transport output ssh on the virtual lines (vty 0 4, vty 5 15).
Why would you need transport output ssh on virtual the lines? Wouldn't you only need the transport input command? When would you ever be going "out" of the virtual lines?

2nd question; Some of these switches don't have either of the above commands, (there is no transport input xxx or transport output xxx), yet it is possible to log into them just fine. Why is that?

mzbagasra

hen configuring the vty lines on a cisco device you usually configure telnet or ssh access to the device as shown below:
# line vty 0 4
# transport input telnet ssh
But what does this following “output” line do?
# transport output telnet ssh
This command allows for you to allow telnetting or ssh access from the device itself. What I mean is if you telnet or ssh to Router1, you can then telnet or ssh from router1 to another device. For security reasons you should disable this if you are planning for outside users to connect to your router.
Disable simple by putting in this command
# line vty 0 4
# transport output none

What is “transport output” used for? - Usual Technology Blog featuring Cisco Networking