— 
# connect
$ssh2->connect($remote_server) or die "\nERROR02 - Unable to connect H
+ost $@ \n";
($code, $error_name, $error_string) = $ssh2->error();
if ($code ne 0)
    {
    &log("error001","code = $code");
    &log("error002","error_name = $error_name");
    &log("error003","error_string = $error_string");
    }

if ($ssh_pattern eq '/passphrase/')
    {
    # authenticate with key and passphrase
    $ssh2->auth_publickey($remote_login, $pub_key_file, $priv_key_file
+, $remote_password) or die "\nERROR03 Unable to login $@ \n";
    ($code, $error_name, $error_string) = $ssh2->error();
    if ($code ne 0)
        {
        &log("error011","code = $code");
        &log("error012","error_name = $error_name");
        &log("error013","error_string = $error_string");
        }
    }
else
    {
    # authenticate with user and password
    $ssh2->auth_password($remote_login,$remote_password) or die "\nERR
+OR04 Unable to login $@ \n";
    ($code, $error_name, $error_string) = $ssh2->error();
    if ($code ne 0)
        {
        &log("error021","code = $code");
        &log("error022","error_name = $error_name");
        &log("error023","error_string = $error_string");
        }
    }

# DE-Block SSH2 for channel open (blocking to 1)
$ssh2->blocking(1);

# open channel 1
$chan1 = $ssh2->channel();
($code, $error_name, $error_string) = $ssh2->error();
if ($code ne 0)
    {
    &log("error031","code = $code");
    &log("error032","error_name = $error_name");
    &log("error033","error_string = $error_string");
    }

# Block SSH2 for channel shell (blocking to 0)
$ssh2->blocking(0);
($code, $error_name, $error_string) = $ssh2->error();
if ($code ne 0)
    {
    &log("error051","code = $code");
    &log("error052","error_name = $error_name");
    &log("error053","error_string = $error_string");
    }
# start channel shell
$chan1->shell();
# send a CR to initialize the session
print $chan1 "\n";
[download]

I'd just like to chime in here that I was experiencing the same problem as madhurikl. I unexplainedly could not establish a connection on my SLES11 SP1 remote hosts. The above code snippet is useful for debugging exactly what the problem is. In my case, SLES was rejecting the authentication.

error021code = -18
error022error_name = LIBSSH2_ERROR_PUBLICKEY_UNRECOGNIZED
error023error_string = Authentication failed (username/password)
[download]

For whatever reason, the Net::SSH2 methods auth and auth_password just don't work on SLES11. However, auth_keyboard works perfectly fine. Problem solved. However, I suspect this should really just be a lesson to both of us to start using keys for authentication in the future.

-Matt