new post: reserve ssh

_posts/2015-02-04-reverse-ssh.md

@@ -0,0 +1,28 @@
+---
+layout: post
+title: "reverse ssh"
+author:
+  display_name: sipp11
+  login: sipp11
+  email: sipp11@gmail.com
+  url: ''
+author_login: sipp11
+author_email: sipp11@gmail.com
+date: Feb 4, 2015
+tags:
+- ssh
+- nat
+---
+There are times when your machine is behind NAT and you couldn't access easily. Unless you have VPN tunneling, it would be tricky. However, reverse `ssh` might be a handy tool.
+
+    | Host A | ----> NAT ---> | Host B |
+
+For above case, you can clearly see that B can access A easily, but reversely, it's not w/o port forwarding blah blah blah. As a result, you can just do reverse `ssh` by start `ssh` from _Host B_ to _Host A_ with command
+
+    $ ssh -NR 8888:localhost:22 user@host-a
+
+Then at _Host A_, you can just `ssh` via port 8888.
+
+    $ ssh user@localhost -p 8888
+
+Violà!