See also VXLAN.
This information largely pertains to OpenSSH, although other SSH agents ought theoretically be able to implement similar functionality.
- Individual TCP ports can be forwarded using the -L and -R options. The latter involves an RFC 4254 "tcpip-forward"-type request.
- Set the ExitOnForwardFailure configuration directive to yes to reliably detect forwarding failures
- X11 can be forwarded using the -X option. This will involve "x11"-type requests.
- Arbitrary Ethernet ("ethernet") or IP ("point-to-point") tunnel devices can be forwarded with -w.
- The remote side must have set PermitTunnel to yes or a value matching the configured TunnelDevice type
- snow tunnels octets under trailing whitespace in ASCII lines
- udptunnel tunnels UDP under TCP
- ptunnel tunnels TCP under ICMP Echo-Request/Echo-Reply
- httptunnel tunnels octets under HTTP
- "An introduction to Linux virtual interfaces: Tunnels" on Red Hat Developer Blog, 2019-05-17