Command to check if the server is not reachable using ssh

I have list for servers say server1, server2, server3.....server20
I want to test the ssh connectivity of each server, if any one of the server is down then ssh connectivity fails and the script results something like echo "serever is not reachable"

Now I m confused using which command shall I check if the server is not reachable using ssh,
can any one suggest the best solution for this so that I can add it in my code

below are the two command I found and how it works:
command1:
success case:

ssh -q user@$server1 exit

bash-3.00$ echo $?
0
failure case:

ssh -q user@$server1000 exit

bash-3.00$ echo $?
255

command2:
success case:

ssh -o ConnectTimeout=3 user@$server1 exit

bash-3.00$ echo $?
0
failure case:

ssh -o ConnectTimeout=3 user@$server1000 exit

ssh: server1000: node name or service name not known
bash-3.00$ echo $?
255

What's the confusion exactly? You've found not one but several ways that work...

I have below three commands can you suggest which is the best and secured, or any other alternate solution for this

ssh -q user@$server1 exit

ssh -o ConnectTimeout=3 user@$server1 exit

ssh -o StrictHostKeyChecking=no -o ConnectTimeout=30 user1@server1