How to automatically switch ssh config based on local subnet?

Question

When I\'m on a certain network (subnet is 10.10.11.x) I need to jump through an intermediate host to reach my destination because of destination port I can\'t change and limited

Answer 1

Based on the answer by Fedor Dikarev, Mike created a bash script named onsubnet:

#!/usr/bin/env bash

if [[ "$1" == "--help" ]] || [[ "$1" == "-h" ]]  || [[ "$1" == "" ]] ; then
  printf "Usage:\n\tonsubnet [ --not ] partial-ip-address\n\n"
  printf "Example:\n\tonsubnet 10.10.\n\tonsubnet --not 192.168.0.\n\n"
  printf "Note:\n\tThe partial-ip-address must match starting at the first\n"
  printf "\tcharacter of the ip-address, therefore the first example\n"
  printf "\tabove will match 10.10.10.1 but not 110.10.10.1\n"
  exit 0
fi

on=0
off=1
if [[ "$1" == "--not" ]] ; then
  shift
  on=1
  off=0
fi

regexp="^$(sed 's/\./\\./g' <<<"$1")"

if [[ "$(uname)" == "Darwin" ]] ; then
  ifconfig | fgrep 'inet ' | fgrep -v 127.0.0. | cut -d ' ' -f 2 | egrep -q "$regexp"
else
  hostname -I | tr -s " " "\012" | fgrep -v 127.0.0. | egrep -q "$regexp"
fi

if [[ $? == 0 ]]; then 
  exit $on
else
  exit $off
fi

Then in his .ssh/config file, he uses Match exec like Jakuje's answer:

Match exec "onsubnet 10.10.1." host my-server
    HostName web.example.com
    Port 1111
    ForwardAgent yes
    ProxyCommand ssh -p 110 -q relay.example.com nc %h %p

Match exec "onsubnet --not 10.10.1." host my-server
    HostName web.example.com
    Port 1111