[vox-tech] How do I make SSH connect anyway if a host's IP has changed?

[Ken Bloom]

A poster on comp.os.linux.misc suggested the following perl script which does what I wanted 
and does it well. I think it's quite a bit more secure than my original attempts to just 
disable SSH's host checking, because I can still verify the authenticity of each ECE machine 
that isn't new.

I had always wondered why the ECS labs didn't employ this kind of strategy for keeping system 
load even, but I think the research it took to get SSH to work well in this situation may at 
least partly be the reason they don't.

------ begin perl script --------------------------
#!/usr/bin/perl -w

use strict;
use Socket;

my(@addrs);
my($dest_name);
my($host) = "snake.ece.ucdavis.edu";

@addrs = (gethostbyname($host))[4];
$dest_name = gethostbyaddr($addrs[0], AF_INET);

exec("ssh @ARGV $dest_name");
------ end perl script ----------------------------

On Tue, 8 Jan 2002 18:34:03 -0800, Ken Bloom <kabloom@ucdavis.edu> wrote:
> On second thought, I think that I'm getting the same IP each time, but different host keys
> each time, considering my errors, and considering that I have 'CheckHostIP no' set. Error is 
> included:
> 
> [SNIP ERROR MESSAGE]
> 
> There was much rejoicing when Ken Bloom <kabloom@ucdavis.edu> spoke thus:
> > The Electrical and Computer Engineering department has set up a system where, by connecting to 
> > the address snake.ece.ucdavis.edu, the department hands off connections to the least busy HP 
> > computer in their lab.  I was trying, today to use ssh to connect to these HP computers by 
> > SSH. The first try, (and some random tries after that), SSH would connect OK. Most other 
> > times, however, the remote computer would fail the test because I was being handed off to a 
> > different HP system.
> > 
> > I am currently trying to connect using a shell script I created named snake:
> > 
> > #! /bin/bash
> > cat > ~/.sshconfig << ENDOFCONFIG
> > StrictHostKeyChecking no
> > CheckHostIP no
> > ENDOFCONFIG
> > ssh -F ~/.sshconfig kabloom@snake.ece.ucdavis.edu
> > 
> > (neither of these configuration options seem to be doing the trick, even after I deleted the 
> > offending key from ~/.ssh/known_hosts)
> > 
> > Is there any way to make SSH ignore the tests that it uses to verify host authenticity when
> > I connect to snake.ece.ucdavis.edu?