---
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!