# A Practical Guide to SSH Tunnels: Local and Remote Port Forwarding > Source: > Published: 2026-06-20 03:55:19+00:00 # A Practical Guide to SSH Tunnels: Local and Remote Port Forwarding SSH is [yet another example](https://iximiuz.com/en/posts/linux-pty-what-powers-docker-attach-functionality/) of an ancient technology that is still in wide use today. It may very well be that learning a couple of SSH tricks is more profitable in the long run than mastering a dozen Cloud Native tools or AI agent frameworks destined to become deprecated next quarter. One of my favorite parts of this technology is SSH Tunnels. With nothing but standard tools and often using just a single command, you can achieve the following: - Access internal VPC endpoints through a public-facing EC2 instance. - Open a `localhost` port of a remote development VM in the local browser. - Expose any local server from a home/private network to the outside world. [Tunnel your browser's debugging port to a remote sandboxed coding agent](/docs/playground-recipes/coding-agent-with-browser-access). And more 😍 But despite the fact that I use SSH Tunnels daily, it always takes me a while to recall the right command. Should it be a Local or a Remote tunnel? What are the flags? Is it a *local_port:remote_port* or the other way around? So, I decided to finally wrap my head around it, and it resulted in a series of labs and a visual cheat sheet. The labs in this tutorial run on an attached playground with four hosts wired into three networks: `internal` - a device on the**home** network`192.168.0.0/24` (a homelab box, a NAS, a printer). Not reachable from the**public** network.`local` - your workstation. Sits on both the**home**`192.168.0.0/24` and the**public**`203.0.113.0/24` networks.`remote` - a public-facing bastion / gateway on the**public**`203.0.113.0/24` network, also connected to a private**vpc**`172.16.0.0/24` .`private` - an internal-only service (a database, an OpenSearch cluster) on the**vpc**`172.16.0.0/24` . Not reachable from the**public** network. You can `ssh` from `local` to `remote` by hostname or IP address - the `local` host key is already trusted on the `remote` machine: ``` ssh remote ssh 203.0.113.30 ``` ## Local Port Forwarding Starting from the one that I use the most. Oftentimes, there might be a service listening on `localhost` or a private interface of a remote machine that I can only SSH to via its public IP. And I desperately need to access this port from my local machine. A few typical examples: - Accessing a private remote database (MySQL, Postgres, Redis, etc) from your laptop using your favorite UI tool. - Using your browser to access a web application exposed only to a private network. - Accessing a container's port from your laptop without publishing it on the server's public interface. All of the above use cases can be solved with a single `ssh` command: ``` ssh -L [local_addr:]local_port:remote_addr:remote_port [user@]sshd_addr ``` The `-L` flag indicates we're starting a *local port forwarding*. What it actually means is: - On your local machine, the SSH client will start listening on `local_port` (likely, on`localhost` , but*it depends*-[check the](https://linux.die.net/man/5/sshd_config#GatewayPorts)).`GatewayPorts` setting - Any traffic to this port will be forwarded to `remote_addr:remote_port` , reached from the remote machine you SSH-ed to. Here is what it looks like on a diagram: **Pro Tip:** Use `ssh -f -N -L` to run the port-forwarding session in the background. ## Lab 1: Using SSH Tunnels for Local Port Forwarding 👨🔬 This lab reproduces the setup from the diagram above. The `remote` host runs a web server bound to `127.0.0.1:80` , and we want to reach it from the `local` workstation. Because the service is bound to the loopback interface, it cannot be reached over the network. From the local host, try to hit the `remote` host's public address: ``` curl 203.0.113.30:80 # remote.public curl: (7) Failed to connect to 203.0.113.30 port 80 after 0 ms: Could not connect to server ``` But from the inside of the remote host, the very same service works just fine: ``` curl localhost:80 Hello from the remote host (localhost-only service). ``` **And here is the trick:** back on the local host, bind the remote's `localhost:80` to the local's `localhost:8080` using local port forwarding: ``` ssh -f -N -L 8080:localhost:80 203.0.113.30 ``` Now you can access the web service on a local port of your workstation: ``` curl localhost:8080 Hello from the remote host (localhost-only service). ``` A slightly more verbose (but more explicit and flexible) way to achieve the same goal: ``` ssh -f -N -L localhost:8080:localhost:80 203.0.113.30 # local remote via ``` ## Local Port Forwarding with a Bastion Host It might not be obvious at first, but the `ssh -L` command allows forwarding a local port to a remote port on *any machine*, not only on the SSH server itself. Notice how the `remote_addr` and `sshd_addr` may or may not have the same value: ``` ssh -L [local_addr:]local_port:remote_addr:remote_port [user@]sshd_addr ``` A remote SSH server used to access private destinations is usually called a [ bastion or jump host](https://en.wikipedia.org/wiki/Bastion_host). This is how I visualize this scenario in my head: I often use the above trick to call endpoints that are accessible from the *bastion host* but not from my laptop (e.g., using an EC2 instance with private and public interfaces to connect to an OpenSearch cluster or any other service deployed fully within a VPC). ## Lab 2: Local Port Forwarding with a Bastion Host 👨🔬 This lab reproduces the setup from the diagram above. The remote target service runs on the `private` host inside an improvised VPC network (`172.16.0.40:80` ), and the former `remote` host acts as our public-facing bastion (jump host) that can reach it. The `local` workstation has no route into the VPC, so it cannot talk to the `private` host directly. From the local host: ``` curl --connect-timeout 3 172.16.0.40:80 # private.vpc curl: (28) Connection timed out after 3002 milliseconds ``` The `remote` bastion, on the other hand, is connected to the VPC and can reach the `private` host. So, we forward a local port through the bastion straight to the private service. From the local host: ``` ssh -f -N -L 8081:172.16.0.40:80 203.0.113.30 ``` Checking that it works - still on the local host: ``` curl localhost:8081 Hello from the private VPC host (172.16.0.40). ``` **Notice that the forwarding target ( 172.16.0.40) and the SSH server (203.0.113.30) are different machines.** The bastion accepts the connection and opens the second hop to the private host on our behalf. A slightly more verbose (but more explicit and flexible) way to achieve the same goal: ``` ssh -f -N -L localhost:8081:172.16.0.40:80 203.0.113.30 # local remote via ``` ## Remote Port Forwarding Another popular (but rather inverse) scenario is when you want to momentarily expose a local service to the outside world. Of course, for that, you'll need a *public-facing ingress gateway server*. And the good news is that any public-facing server with an SSH daemon on it can be used as such a gateway: ``` ssh -R [remote_addr:]remote_port:local_addr:local_port [user@]gateway_addr ``` The above command looks no more complicated than its `ssh -L` counterpart. But there is a pitfall... **By default, the above SSH tunnel will allow using only the gateway's localhost as the remote address.** In other words, your local port will become accessible only from inside the gateway server itself, which is most likely not what you actually need. For instance, I typically want to use the gateway's public address as the remote address to expose my local services to the public Internet. For that, the SSH server needs to be configured with the [ GatewayPorts yes](https://linux.die.net/man/5/sshd_config#GatewayPorts) setting. Here is what remote port forwarding can be used for: - Exposing a dev service from your laptop to the public Internet for a quick demo. - Exposing your homelab to the public Internet (for arbitrary purposes). [Tunneling your local browser's debugging port to a remote and/or sandboxed coding agent](/docs/playground-recipes/coding-agent-with-browser-access). Here is how the remote port forwarding can be visualized: **Pro Tip:** Use `ssh -f -N -R` to run the port-forwarding session in the background. ## Lab 3: Using SSH Tunnels for Remote Port Forwarding 👨🔬 This lab reproduces the setup from the diagram above. The `local` workstation runs a web server bound to `127.0.0.1:80` , and we want to expose it to the outside through the public-facing `remote` gateway. The service is bound to the loopback interface, so right now nobody but the `local` machine itself can reach it. Try accessing it from the remote machine: ``` curl --connect-timeout 3 203.0.113.20:80 # local.public curl: (7) Failed to connect to 203.0.113.20 port 80 after 0 ms: Could not connect to server ``` We want to expose it through the `remote` gateway and consume it from the `private` host. The `remote` gateway already has `GatewayPorts yes` in its `sshd_config` , so we can ask it to listen on all of its interfaces (`0.0.0.0` ) and forward the traffic back to us. **However, the local machine has to establish the tunnel first**. From the local host, start the remote port forwarding: ``` ssh -f -N -R 0.0.0.0:8080:localhost:80 203.0.113.30 # remote local via ``` Now the local web service is published on the gateway's interfaces. Let's confirm it from a *third* machine - the private host, which can reach the `remote` gateway over the VPC: ``` curl 172.16.0.30:8080 # remote.vpc Hello from your local workstation (localhost-only service). ``` ## Remote Port Forwarding to a Home or Private Network Similar to local port forwarding, remote port forwarding has its own *bastion or jump host* mode. But this time, the machine with the SSH client (e.g., your dev laptop) plays the role of the jump host. In particular, it allows exposing ports of a home (or private) network reachable from your laptop to the outside world through a remote SSH server acting as an ingress gateway: ``` ssh -R [remote_addr:]remote_port:local_addr:local_port [user@]gateway_addr ``` Looks almost identical to the simple remote SSH tunnel, but the `local_addr:local_port` pair becomes the address of a device in the home network. Here is how it can be depicted on a diagram: I typically use my laptop as a thin client and the actual development happens on a remote server. Sometimes, such a remote server can reside in my home network and have no or restricted Internet access (for extra isolation). This is when I may want to rely on remote port forwarding to expose a service from a home server to the public Internet, using my laptop that can access both the internal dev server and the remote SSH server (ingress gateway) as a jump host. ## Lab 4: Remote Port Forwarding from a Home/Private Network 👨🔬 This lab reproduces the setup from the diagram above. The service we want to expose runs on the `internal` host inside an isolated home network (`192.168.0.10:80` ). Our `local` workstation can reach the home network and also has SSH access to the public-facing `remote` gateway, so it plays the role of a jump host. The `local` host can reach the `internal` service over the home network. From the local host: ``` curl 192.168.0.10:80 # internal.home Hello from the internal home-network host (192.168.0.10). ``` From the outside, though, the `internal` device is invisible. Try accessing it from the remote host: ``` curl --connect-timeout 3 192.168.0.10:80 # internal.home curl: (28) Connection timed out after 3001 milliseconds ``` The `remote` host has no route into the home network, so the request simply times out. Now, from the local host, **start the remote port forwarding from the remote gateway to the internal device**. The forwarding target ( `192.168.0.10` ) is resolved by the SSH client, i.e., from the `local` host's point of view: ``` ssh -f -N -R 0.0.0.0:8081:192.168.0.10:80 203.0.113.30 # remote local via ``` Finally, validate that the home-network service became accessible on the gateway - from the private host, which reaches the gateway over the VPC: ``` curl 172.16.0.30:8081 # remote.vpc Hello from the internal home-network host (192.168.0.10). ``` ## Dynamic Local Port Forwarding This forwarding mode is less transparent for the clients, but it is also significantly more flexible than regular local port forwarding. Instead of wiring a local port to a single remote destination (like `ssh -L` does), **dynamic (local) port forwarding** turns the SSH client into a local [SOCKS proxy](https://en.wikipedia.org/wiki/SOCKS). Any application that can speak SOCKS can then send traffic through it, choosing the actual destination host and port *per connection* - they will be sent over to the SSH server, which will resolve the destination and establish the connection: ``` ssh -D [local_addr:]local_port [user@]sshd_addr ``` When the `-D` flag is used, the SSH client on your machine starts a SOCKS proxy listening on `local_port` (on `localhost` by default). Each connection made through the proxy is forwarded to whatever address the SOCKS client asks for, reached from the `sshd_addr` machine. In other words, it's like `ssh -L` , but you don't have to specify a single `remote_addr:remote_port` upfront, because the SOCKS protocol allows specifying the destination at the beginning of each connection (via a few extra bytes sent right before the payload). One (local) proxied port gives you access to *every* host and port reachable from the (remote) SSH server. Here is what dynamic port forwarding can be used for: - Calling APIs in a private network through a bastion, without a separate tunnel per service. - Browsing internal web apps in a remote network via a single jump host. - Reaching a fleet of VPC endpoints from your laptop through one EC2 instance. **Pro Tip:** Use `ssh -f -N -D` to run the SOCKS proxy in the background. ## Lab 5: Using SSH Tunnels for Dynamic Port Forwarding 👨🔬 This is the bastion scenario from Lab 2 again, except this time we won't pin the tunnel to a single destination. First, let's make sure we cannot reach the `private` destination from the local machine: ``` curl --connect-timeout 3 172.16.0.40:80 # private.vpc curl: (28) Connection timed out after 3002 milliseconds ``` Now, on the local host, start a SOCKS proxy through the `remote` host: ``` ssh -f -N -D 1080 203.0.113.30 # remote.public ``` If you point `curl` at the proxy to reach the `private` VPC service, the request will come through: ``` curl --socks5-hostname localhost:1080 172.16.0.40:80 # via private.vpc Hello from the private VPC host (172.16.0.40). ``` Note that unlike with `ssh -L` , the client - curl in this case - must be able to speak SOCKS (see the `--socks5-hostname` flag). The same SOCKS proxy reaches *any* host the `remote` machine can - including a *second* VPC host - without setting up a separate tunnel, try reaching the `private-2` machine: ``` curl --socks5-hostname localhost:1080 172.16.0.50:80 # via private-2.vpc Hello from the second private VPC host (172.16.0.50). ``` With `ssh -L` , reaching both private hosts would have meant two separate tunnels (one per `remote_addr:remote_port` ). A single `ssh -D` proxy covers the whole network behind the bastion. ## Dynamic Remote Port Forwarding Just like `ssh -L` has a dynamic sibling in `ssh -D` , the `ssh -R` command has its own dynamic mode. If you drop the fixed destination from `-R` and pass only a port, OpenSSH turns the **SSH server** itself into a SOCKS proxy. It's the exact mirror of `-D` : this time the proxy lives on the gateway, and every connection made through it is tunneled back to the `ssh` client and resolved from *its* point of view: ``` ssh -R [bind_address:]port [user@]gateway_addr ``` The `-R` flag **with no destination means**: - On the remote gateway, the SSH server starts a SOCKS proxy listening on `port` (on the gateway's`localhost` by default, or on all interfaces with`GatewayPorts yes` ). - Each connection made through the proxy is tunneled back to the `ssh` client and forwarded to whatever address the SOCKS client asks for, reached from the client's side. It's like a regular `ssh -R` , but you don't have to choose a single `local_addr:local_port` upfront. One proxy on the gateway exposes *every* host and port reachable from the `ssh` client - for example, an entire home network. Remote dynamic forwarding requires OpenSSH 7.6 or newer on the client. As with a regular `ssh -R` , binding the proxy to a non-loopback address on the gateway needs `GatewayPorts yes` in its `sshd_config` . **Pro Tip:** Use `ssh -f -N -R` to run the SOCKS proxy in the background. ## Lab 6: Using SSH Tunnels for Remote Dynamic Port Forwarding 👨🔬 This is the home-network scenario from Lab 4 again - we want to expose devices that only `local` can reach through the public-facing `remote` gateway - except this time a single proxy covers all of them. First, let's make sure we cannot reach the `internal` host from the private machine: ``` curl 192.168.0.10:80 # internal.home curl: (7) Failed to connect to 192.168.0.10 port 80 after 0 ms: Could not connect to server ``` Now, from the local host, turn the `remote` gateway into a SOCKS proxy, and establish a tunnel with it: ``` ssh -f -N -R 0.0.0.0:1080 203.0.113.30 # remote.public ``` To recheck the connectivity, from the private host again, use the gateway's proxy to reach the `internal` home device: ``` curl --socks5-hostname 172.16.0.30:1080 192.168.0.10:80 # via internal.home Hello from the internal home-network host (192.168.0.10). ``` The same proxy reaches anything the `ssh` client (`local` ) can - including its own loopback service: ``` curl --socks5-hostname 172.16.0.30:1080 127.0.0.1:80 # via local's localhost Hello from your local workstation (localhost-only service). ``` ## Summarizing Here is a quick recap and a couple of mnemonics to help you memorize the SSH tunneling commands: **Local port forwarding**(`ssh -L` ) makes a remote service available on a local port.**Remote port forwarding**(`ssh -R` ) makes a local service available on a remote port.**Dynamic local port forwarding**(`ssh -D` ) turns the local`ssh` client into a SOCKS proxy.**Dynamic remote port forwarding**(`ssh -R` with no destination) turns the`sshd` server into a SOCKS proxy.- Local port forwarding ( `ssh -L` ) implies it's the`ssh` client that starts listening on a new port. - Remote port forwarding ( `ssh -R` ) implies it's the`sshd` server that starts listening on an extra port. - The word **local** can mean either the**SSH client machine** or an internal host accessible from it. - The word **remote** can mean either the**SSH server machine (sshd)** or any host accessible from it. - The mnemonics are *ssh*and**-L****l** ocal:remote*ssh*and it's always the left-hand side that opens a new port.**-R****r** emote:local Hope the above materials helped you a bit with becoming a master of SSH Tunnels 🧙 ## Practice Reinforce your learning by solving these practical challenges: ## Resources [SSH Tunneling Explained](https://goteleport.com/blog/ssh-tunneling-explained/)by networking gurus from Teleport.[SSH Tunneling: Examples, Command, Server Config](https://www.ssh.com/academy/ssh/tunneling-example)by SSH Academy. ### About the Author Writes about Frequently covers