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Net::Telnet::Cisco(3) User Contributed Perl DocumentationNet::Telnet::Cisco(3)

       Net::Telnet::Cisco - interact with a Cisco router

	 use Net::Telnet::Cisco;

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

	 # Execute a command
	 my @output = $session->cmd('show version');
	 print @output;

	 # Enable mode
	 if ($session->enable("enable_password") ) {
	     @output = $session->cmd('show privilege');
	     print "My privileges: @output\n";
	 } else	{
	     warn "Can't enable: " . $session->errmsg;


       Net::Telnet::Cisco provides additional functionality to Net::Telnet for
       dealing with Cisco routers.

       cmd() parses router-generated error messages - the kind that begin with
       a '%' - and stows them in $obj->errmsg(), so that errmode can be	used
       to perform automatic error-handling actions.

       Before you use Net::Telnet::Cisco, you should have a good understanding
       of Net::Telnet, so read it's documentation first, and then come back
       here to see the improvements.

       Some things are easier to accomplish with UCD's C-based SNMP module, or
       the all-perl Net::SNMP. SNMP has	three advantages: it's faster, handles
       errors better, and doesn't use any VTYs on the router. SNMP does	have
       some limitations, so for	anything you can't accomplish with SNMP,
       there's Net::Telnet::Cisco.

       new - create new	Net::Telnet::Cisco object
	       $session	= Net::Telnet::Cisco->new(
		   [Always_waitfor_prompt => $boolean,]	     # 1
		   [Autopage		  => $boolean,]	     # 1
		   [Ignore_warnings	  => $boolean,]	     # 0
		   [More_prompt		  => $matchop,]	     # '/(?m:^\s*--More--)/',
		   [Normalize_cmd	  => $boolean,]	     # 1
		   [Send_wakeup		  => $when,]	     # 0
		   [Waitfor_pause	  => $milliseconds,] # 0.1
		   [Warnings		  => $matchop,]	     # see docs

		   # Net::Telnet arguments

	   Creates a new object. Read `perldoc perlboot` if you	don't
	   understand that.

       login - login to	a router
	       $ok = $obj->login($username, $password);

	       $ok = $obj->login([Name	   => $username,]
				 [Password => $password,]
				 [Passcode => $passcode,] # for	Secur-ID/XTACACS
				 [Prompt   => $match,]
				 [Timeout  => $secs,]);

	   All arguments are optional as of v1.05. Some	routers	don't ask for
	   a username, they start the login conversation with a	password

       cmd - send a command
	       $ok = $obj->cmd($string);
	       $ok = $obj->cmd(String	=> $string,
			       [Output	=> $ref,]
			       [Prompt	=> $match,]
			       [Timeout	=> $secs,]
			       [Cmd_remove_mode	=> $mode,]);

	       @output = $obj->cmd($string);
	       @output = $obj->cmd(String   => $string,
				   [Output  => $ref,]
				   [Prompt  => $match,]
				   [Timeout => $secs,]
				   [Cmd_remove_mode => $mode,]
				   [Normalize_cmd => $boolean,]);

	   Normalize_cmd has been added	to the default Net::Telnet args. It
	   lets	you temporarily	change whether backspace, delete, and kill
	   characters are parsed in the	command	output.	(This is performed by

       prompt -	return control to the program whenever this string occurs in
       router output
	       $matchop	= $obj->prompt;

	       $prev = $obj->prompt($matchop);

	   The default cmd_prompt changed in v1.05. It's suitable for matching
	   prompts like	"router$ ", "router# ",	"router> (enable) ", and
	   "router(config-if)# "

	   Let's take a	closer look, shall we?

	     (?m:	   # Net::Telnet doesn't accept	quoted regexen (i.e. qr//)
		       # so we need to use an embedded pattern-match modifier
		       # to treat the input as a multiline buffer.

	       ^	   # beginning of line

		 [\w.-]+       # router	hostname

		 \s?	   # optional space

		 (?:	   # Strings like "(config)" and "(config-if)",	"(config-line)",
		       # and "(config-router)" indicate	that we're in privileged
		   \(config[^\)]*\) # EXEC mode	(i.e. we're enabled).
		 )?	   # The middle	backslash is only there	to appear my syntax
		       # highlighter.

		 \s?	   # more optional space

		 [\$#>]	       # Prompts typically end with "$", "#", or ">". Backslash
		       # for syntax-highlighter.

		 \s?	   # more space	padding

		 (?:	   # Catalyst switches print "(enable)"	when in	privileged
		   \(enable\)  # EXEC mode.

		 \s*	   # spaces before the end-of-line aren't important to us.

	       $	   # end of line

	     )	       # end of	(?m:

	   The default prompt published	in 1.03	was
	   "/^\s*[\w().-]*[\$#>]\s?(?:\(enable\))?\s*$/". As you can see, the
	   prompt was drastically overhauled in	1.05. If your code suddenly
	   starts timing out after upgrading Net::Telnet::Cisco, this is the
	   first thing to investigate.

       enable -	enter enabled mode
	       $ok = $obj->enable;

	       $ok = $obj->enable($password);

	       $ok = $obj->enable([Name	=> $name,] [Password =>	$password,]
			      [Passcode	=> $passcode,] [Level => $level,]);

	   This	method changes privilege level to enabled mode,	(i.e. root)

	   If a	single argument	is provided by the caller, it will be used as
	   a password. For more	control, including the ability to set the
	   privilege-level, you	must use the named-argument scheme.

	   enable() returns 1 on success and undef on failure.

       is_enabled - Am I root?
	       $bool = $obj->is_enabled;

	   A trivial check to see whether we have a root-style prompt, with
	   either the word "(enable)" in it, or	a trailing "#".

	   Warning: this method	will return false positives if your prompt has
	   "#"s	in it. You may be better off calling "$obj->cmd("show
	   privilege")"	instead.

       disable - leave enabled mode
	       $ok = $obj->disable;

	   This	method exits the router's privileged mode.

       fhopen -	use already open filehandle for	I/O
	       $ok = $obj->fhopen($fh);

	   This	method associates the open filehandle $fh with $obj for
	   further I/O.	 Filehandle $fh	must already be	opened.

	   The value 1 is returned success, the	error mode action is performed
	   on failure.

       ios_break - send	a break	(control-^)
	       $ok = $obj->ios_break;

	   You may have	to use errmode(), fork,	or threads to break at the an
	   appropriate time.

       last_cmd	- displays the last command
	       $match =	$obj->last_cmd;

	   last_cmd() will return '' if	the program does not yet have a	last

       last_prompt - displays the last prompt matched by prompt()
	       $match =	$obj->last_prompt;

	   last_prompt() will return ''	if the program has not yet matched a

       always_waitfor_prompt - waitfor and cmd prompt behaviour
	       $boolean	= $obj->always_waitfor_prompt;

	       $boolean	= $obj->always_waitfor_prompt($boolean);

	   Default value: 1

	   If you pass a Prompt	argument to cmd() or waitfor() a String	or
	   Match, they will return control on a	successful match of your
	   argument(s) or the default prompt. Set always_waitfor_prompt	to 0
	   to return control only for your arguments.

	   This	method has no effect on	login(). login() will always wait for
	   a prompt.

       waitfor_pause - insert a	small delay before waitfor()
	       $boolean	= $obj->waitfor_pause;

	       $boolean	= $obj->waitfor_pause($milliseconds);

	   Default value: 0.1

	   In rare circumstances, the last_prompt is set incorrectly. By
	   adding a very small delay before calling the	parent class's
	   waitfor(), this bug is eliminated. If you ever find reason to
	   modify this from it's default setting, please let me	know.

       autopage	- Turn autopaging on and off
	       $boolean	= $obj->autopage;

	       $boolean	= $obj->autopage($boolean);

	   Default value: 1

	   IOS pages output by default.	It expects human eyes to be reading
	   the output, not programs. Humans hit	the spacebar to	scroll page by
	   page	so autopage() mimicks that behaviour. This is the slow way to
	   handle paging. See the Paging EXAMPLE for a faster way.

       normalize_cmd - Turn normalization on and off
	       $boolean	= $obj->normalize_cmd;

	       $boolean	= $obj->normalize_cmd($boolean);

	   Default value: 1

	   IOS clears '--More--' prompts with backspaces (e.g. ^H). If you're
	   excited by the thought of having raw	control	characters like	^H
	   (backspace),	^? (delete), and ^U (kill) in your command output,
	   turn	this feature off.

	   Logging is unaffected by this setting.

       more_prompt - Matchop used by autopage()
	       $matchop	= $obj->prompt;

	       $prev = $obj->prompt($matchop);

	   Default value: '/(?m:\s*--More--)/'.

	   Please email	me if you find others.

       send_wakeup - send a newline to the router at login time
	       $when = $obj->send_wakeup;

	       $when = $obj->send_wakeup( 'connect' );
	       $when = $obj->send_wakeup( 'timeout' );
	       $when = $obj->send_wakeup( 0 );

	   Default value: 0

	   Some	routers	quietly	allow you to connect but don't display the
	   expected login prompts. Sends a newline in the hopes	that this
	   spurs the routers to	print something.

	   'connect' sends a newline immediately upon connection.  'timeout'
	   sends a newline if the connection timeouts.	0 turns	this feature

	   I understand	this works with	Livingston Portmasters.

       ignore_warnings - Don't call error() for	warnings
	       $boolean	= $obj->ignore_warnings;

	       $boolean	= $obj->ignore_warnings($boolean);

	   Default value: 0

	   Not all strings that	begin with a '%' are really errors. Some are
	   just	warnings. By setting this, you are ignoring them. This will
	   show	up in the logs,	but that's it.

       warnings	- Matchop used by ignore_warnings().
	       $boolean	= $obj->warnings;

	       $boolean	= $obj->warnings($matchop);

	   Default value:

	       /(?mx:^%	Unknown	VPN
		    |^%IP routing table	VRF.* does not exist. Create first$
		    |^%No CEF interface	information
		    |^%No matching route to delete$
		    |^%Not all config may be removed and may reappear after reactivating

	   Not all strings that	begin with a '%' are really errors. Some are
	   just	warnings. Cisco	calls these the	CIPMIOSWarningExpressions.

       v1.08 added internal autopaging support to cmd(). Whenever a '--Page--'
       prompt appears on the screen, we	send a space right back. It works, but
       it's slow. You'd	be better off sending one of the following commands
       just after login():

	 # To a	router
	 $session->cmd('terminal length	0');

	 # To a	switch
	 $session->cmd('set length 0');

       Want to see the session transcript? Just	call input_log().

	 my $session = Net::Telnet::Cisco->new(Host => $router,
			   Input_log =>	"input.log",

       See input_log() in Net::Telnet for info.

       Input logs are easy-to-read translated transcripts with all of the
       control characters and telnet escapes cleaned up. If you	want to	view
       the raw session,	see dump_log() in Net::Telnet. If you're getting
       tricky and using	print()	in addition to cmd(), you may also want	to use

   Big output
       Trying to dump the entire BGP table? (e.g. "show	ip bgp") The default
       buffer size is 1MB, so you'll have to increase it.

	 my $MB	= 1024 * 1024;
	 $session->max_buffer_length(5 * $MB);

   Sending multiple lines at once
       Some commands like "extended ping" and "copy" prompt for	several	lines
       of data.	It's not necessary to change the prompt	for each line.
       Instead,	send everything	at once, separated by newlines.


	 router# ping
	 Protocol [ip]:
	 Target	IP address:
	 Repeat	count [5]: 10
	 Datagram size [100]: 1500
	 Timeout in seconds [2]:
	 Extended commands [n]:
	 Sweep range of	sizes [n]:

       Try this:

	 my $protocol  = ''; # default value
	 my $ip	      =	'';
	 my $repeat    = 10;
	 my $datagram  = 1500;
	 my $timeout   = ''; # default value
	 my $extended  = ''; # default value
	 my $sweep     = ''; # default value


       If you prefer, you can put the cmd on a single line and replace every
       static newline with the "\n" character.


		 . "$timeout\n$extended\n$sweep\n");

   Backup via TFTP
       Backs up	the running-confg to a TFTP server. Backup file	is in the form
       "router-confg". Make sure that file exists on the TFTP server or	the
       transfer	will fail!

	 my $backup_host  = "";
	 my $device	  = "";
	 my $type	  = "router"; #	or "switch";
	 my $ios_version  = 12;

	 my @out;
	 if ($type eq "router")	{
	     if	($ios_version >= 12) {
		 @out =	$session->cmd("copy system:/running-config "
		       . "tftp://$backup_host/$device-confg\n\n\n");
	     } elsif ($ios_version >= 11) {
		 @out =	$session->cmd("copy running-config tftp\n$backup_host\n"
		       . "$device-confg\n");
	     } elsif ($ios_version >= 10) {
		 @out =	$session->cmd("write net\n$backup_host\n$device-confg\n\n");
	 } elsif ($type	eq "switch") {
	     @out = $session->cmd("copy	system:/running-config "
		       . "tftp://$backup_host/$device-confg\n\n\n");


   Mailing lists
       nettelnetcisco-announce is for important	security bulletins and
       upgrades. Very low traffic, no spam, HIGHLY RECOMMENDED!

       nettelnetcisco-users is for usage discussion, help, tips, tricks, etc.

       nettelnetcisco-devel is for uber-hackers; you know who you are.

   Help/discussion forums

   Bug tracker



       UCD NetSNMP -

       RAT/NCAT	-

AUTHOR $Date: 2002/06/18 17:17:03	$

       It would	greatly	amuse the author if you	would send email to him	and
       tell him	how you	are using Net::Telnet::Cisco.

       As of Mar 2002, 170 people have emailed me. N::T::C is used to help
       manage over 14,000 machines! Keep the email rolling in!

       The following people understand what Open Source	Software is all	about.
       Thanks Brian Landers, Aaron Racine, Niels van Dijke, Tony Mueller,
       Frank Eickholt, Al Sorrell, Jebi	Punnoose, Christian Alfsen, Niels van
       Dijke, Kevin der	Kinderen, Ian Batterbee, Leonardo Cont,	Steve Meier,
       and Andre Bonhote.

       Institutions: #perl,,,	the
       geeks at, and

       Send in a patch and we can make the world a better place.

       Copyright (c) 2000-2002 Joshua Keroes, Electric Lightwave Inc.  All
       rights reserved.	This program is	free software; you can redistribute it
       and/or modify it	under the same terms as	Perl itself.

perl v5.32.1			  2017-09-11		 Net::Telnet::Cisco(3)


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