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Basil A
Asked: 2020-04-30 05:41:38 +0800 CST

What configurations do I need to enable on sshd_config to be able to use it as a jump node server?

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What configurations do I need to enable on sshd_config on a jump node server to be able to utilize that server using ProxyJump.

ssh

1 Answers

  1. Best Answer

    You must enable port forwarding with AllowTcpForwarding using at least local or else yes (which is the default):

    Specifies whether TCP forwarding is permitted. The available options are yes (the default) or all to allow TCP forwarding, no to prevent all TCP forwarding, local to allow local (from the perspective of ssh(1)) forwarding only or remote to allow remote forwarding only.

    That's because the ProxyJump option is just an optimized method (using pipes instead of tcp or unix sockets on the local side) from the client to ask the server to forward a tcp port. In the end the server is just receiving the same request and doing the same treatment.

    Running:

    $ ssh -J proxyhost destinationhost

    currently spawns a subprocess (both are connected with two pairs of pipes for a full-duplex result):

    ssh -W destinationhost:22 proxyhost

    -W is an ssh option similar to -L:

    -W host:port

    Requests that standard input and output on the client be forwarded to host on port over the secure channel. Implies -N, -T, ExitOnForwardFailure and ClearAllForwardings, though these can be overridden in the configuration file or using -o command line options.

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