Kinda simple but awesome way to ssh to hosts by IP but using the known_hosts name cache, e.g. if DNS is down or otherwise not resolving.

ssh-by-ip-cache.sh

# yes, there are many ways to simpify this, but it's just a quick hack...
getsship() { fgrep $( fgrep  "$1"  ~/.ssh/known_hosts |head -1| awk '{print $3}') ~/.ssh/known_hosts | egrep -o '(^[0-9\.]+)'; }
sshbyip() { name=$1; shift; ssh $(getsship "$name") "$@"; }

# and if you want tab completion (assuming _ssh tab completion loaded)
# this test doesn't work, not sure yet what best way to copy the complete from 'ssh' comand is yet given how it is dynamically loaded.
# and not avaialble at .bashrc loading..  if type _ssh >/dev/null; then
if shopt -q progcomp && [ -n "$BASH_COMPLETION_COMPAT_DIR" ]; then
  complete -F _ssh sshbyip
  complete -F _ssh getsship
fi

# Usage:
#  $ sshbyip somecachedhostname
#  $ ssh dave@$(getsship daveshost)