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Jumphost - Pull Switch Configs with Perl

I have a few jumphosts that let I use to ssh into and then access network switches. I used to use rancid and have like 6 rancid more. I wrote my own switch backup script. I wont go into the details of my script BUT i thought this ssh trick was worth a look with Perl.

Net::OpenSSH <--Awesome

This snippet of code does a ping check using a Jump Host. This is fairly easy to do using just ssh without Perl. But if I wanted to use Expect, I need Net::OpenSSH instance to pass into it.

The Modules I use for Expect are:
I actually wrap these in a MCE::Loop to do 10 or so switches at a time. MCE::Loop is always my go to for my loops that need to be sped up. Im pulling 30 switches in under a minute.

I am going to break up this snippet and explain whats going on.

Identify your two ips.

use Net::OpenSSH;
use Modern::Perl;

my $ip = ''; #switch ip
my $proxy_ip = ''; #jump host ip

sub pingCheck ( $ip, $proxy_ip) {
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This example uses a ssh key pair, you can change key_path for password and put the ssh password in.

    my %opts = (host => $proxy_ip, user => 'myuser', key_path => '/home/myuser/.ssh/id_rsa');
    my $ssh_proxy = Net::OpenSSH->new(%opts);
    $ssh_proxy->error and die "Couldn't establish SSH connection: ". $ssh_proxy->error;

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Now I run a ping command on the jump host.

    my @ping = $ssh_proxy->capture("ping -c 1 ".$ip);

    foreach(@ping) {
        if( $_ =~ m/^1\spackets transmitted/ && $_ =~ m/\s0\% packet loss/ ) {
            return 1;
        elsif($_ =~ m/^1\spackets transmitted/) {
            return 0;
if(pingCheck()) {
    warn "YES";
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If i needed to access the $ip using a different port instead of ping, lets say it was telnet.

$ssh_proxy->system({ssh_opts => ['-O','forward','-L127.0.0.1:8000:'.$ip.':23']});
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I can then do telnet localhost 8000 and it will connect to the $ip.

This might be confusing for some, its technical and geared for network engineers that can do programming. If you are interested in how i pull switches, you can ask and i'll hint at how to put something together.

Top comments (2)

szabgab profile image
Gabor Szabo


I personally prefer not to use $_ explicitly. I'd either get rid of it, and I think in this code one could just write the m/.../.../ statements without the $_ =~ and they would work, OR I'd use a variable with a meaningful name.

scotticles profile image

I didnt know you could just do m/../../ i'll try that on monday and tweak it, im so used to using $_ for little loops but i should probably start using a named variable instead so people understand whats happening. Thanks! Good suggestions.