Software Development

Older switches don't have the nifty 'interface range' command for applying the same configuration to multiple interfaces at the same time. On older style 48 port switches, it can be a boring task to update all interfaces with, say, a new vlan assignment.

I was thinking of doing an Expect script to perform the task. I tackled it once upon a time, and did come up with a working example, but it took a while to get used to the nuances of the Expect language.

Having more skills in Perl, and realizing that there is a CPAN add-on for Cisco devices, I recently did something up in Perl. The example below connects to a switch, and for each of 48 interfaces, it defaults it and then applies a new vlan.

By creating an array of devices, and if they have common usernames and passwords, or are authenticated through TACACS, the same commands could be applied to a range of devices in one easy run.

use strict;

use Net::Telnet::Cisco;

my $postDevice = 'bmsw08';
my $postCommand = 'sho inter status';

  my $session = Net::Telnet::Cisco->new(
    Host => $postDevice
    );
#  $session->login( '', 'password' );
  $session->login( 'username', 'password' );
  $session->enable('enable');

  my @output;
#  my @output = $session->cmd(String => $postCommand );
#  print @output;

   print $session->cmd( String => 'config t' );

   for ( my $i = 1; $i <= 48; $i++ ) {
     print $session->cmd( String => "inter f0/$i" );
     print $session->cmd( String => "default desc" );
     print $session->cmd( String => "swi acc vlan 103" );
   }

  $session->close();

There are two types of logins, one with a username and password, and one with just a password. An Enable is used in either case.