When I asked, there were many people who didn't know much, so I will write it.
With just this, it's a little difficult to understand. In other words, forward processing with the same port number is possible for multiple destinations.
For example, communication for server A to 443 (https) and communication for server B to 443 (https) without adding a physical NIC and without changing the local monitoring port number. You can forward with a single command on one server. Of course, it is the same for any port number, not just 443.
# ifconfig eth0 aaa.aaa.aaa.aaa ...
And as if it was set to the physical NIC
# ifconfig eth0:0 xxx.xxx.xxx.xxx
# ifconfig eth0:1 yyy.yyy.yyy.yyy
# ifconfig eth0:2 zzz.zzz.zzz.zzz
And suppose you have added an IP alias.
Here, the privileged port is root,
# ssh -L aaa.aaa.aaa.aaa:443:localhost:1443 -L xxx.xxx.xxx.xxx:443:localhost:2443 -L yyy.yyy.yyy.yyy:443:localhost:3443 -L zzz.zzz.zzz.zzz:443:localhost:4443 user@server
It means that you can do it.
Of course, after this, we will forward to the target server by multi-stage transfer, but
The advantage of being able to transfer on is effective when you are using an application whose communication port cannot be changed. ** ** In particular, Windows apps often cannot change ports. ``
Even in such a case, you can use 443 of aaa.aaa.aaa.aaa and 443 of xxx.xxx.xxx.xxx at the same time **! ** **
You can give multiple IP addresses to a physical NIC in the network settings of the control panel, right?
Here, ** Cygwin's ssh can do the same thing **.
[To use OpenBlocks safely without using an SSL-VPN device (use OpenBlocks like a simple VPN device)](https: / /qiita.com/shinya-kurioka/items/bb8b1ebce897d0a26965) It can be used remotely from a remote location to multiple servers on the internal network, ** more like a VPN **.