nemasys has asked for the wisdom of the Perl Monks concerning the following question:

Hi, I am trying to adjust a Cisco IOS config and need to add some extra lines of commands and they need to be added to a specific area in the IOS config

The x's are the IP address on the interface statement and i need to find interfaces that already have the ip helper-address statement defined and then append two more ip helper-address statements after the one that is already defined. The other issue is there are a number of interfaces in the IOS config that will need these extra ip helper-address applied. The common factor is any interfaces that have the ip helper-address defined add the extra two, that is what I require. 

Extra IOS commands to be added:

ip helper-address x.x.x.x
ip helper-address x.x.x.x

IOS config data file example:

!
interface GigabitEthernet1/0/1
 description *** VLAN 1 **
 no switchport
 ip address x.x.x.x x.x.x.x
 ip helper-address x.x.x.x
 no ip redirects
 no ip proxy-arp
 service-policy input U_SET_DSCP
 ip ospf cost 10
 srr-queue bandwidth share 1 3 97 1
 priority-queue out 
 standby ip x.x.x.x
 standby timers 1 3
 standby priority 95
 standby preempt
!

Any help would be much appreciated.

J

  • Comment on Appending data to a file in a specific location

Replies are listed 'Best First'.
Re: Appending data to a file in a specific location
by toolic (Bishop) on May 01, 2009 at 16:53 UTC
    Loop through the lines of your input file, search for your magic string with a regular expression, then inject the extra lines. Something like this should get you started: 
    use strict;
use warnings;

while (<DATA>) {
    if (/ip helper-address/) {
        print;
        print " ip helper-address x.x.x.x\n";
        print " ip helper-address x.x.x.x\n";
    }
    else {
        print;
    }
}

__DATA__
!
interface GigabitEthernet1/0/1
 description *** VLAN 1 **
 no switchport
 ip address x.x.x.x x.x.x.x
 ip helper-address x.x.x.x
 no ip redirects
 no ip proxy-arp
 service-policy input U_SET_DSCP
 ip ospf cost 10
 srr-queue bandwidth share 1 3 97 1
 priority-queue out 
 standby ip x.x.x.x
 standby timers 1 3
 standby priority 95
 standby preempt
!

    [download]
[reply]
[d/l]

      Hi,

      Thanks for the reply, I had used this code before, but I should have explained that you might get multiple ip helper-address statements one below the other and if you have multiple, then you will be applying the print statement more than once which is not the what I need. Is there a way to just apply the two new ip helper-address statments below more than one that has been already defined

      Example: 

      !
interface GigabitEthernet1/0/1
 description *** VLAN 1 **
 no switchport
 ip address x.x.x.x x.x.x.x
 ip helper-address x.x.x.x
 ip helper-address x.x.x.x
 no ip redirects
 no ip proxy-arp
 service-policy input U_SET_DSCP
 ip ospf cost 10
 srr-queue bandwidth share 1 3 97 1
 priority-queue out 
 standby ip x.x.x.x
 standby timers 1 3
 standby priority 95
 standby preempt
!

      Thanks in advance

      James

[reply]
Re: Appending data to a file in a specific location
by spectre9 (Beadle) on May 01, 2009 at 18:52 UTC

    One of the earliest uses I made of Perl was on Cisco IOS. Initially, to parse RADIUS log output, but later on, I used Expect.pm and telnet to automatically fetch router configurations, modify them, and submit them back to the router (actually, just made the IOS changes in-situ). Anyway, thought I would point out this module as it may be relevant to your task.

    "Strictly speaking, there are no enlightened people, there is only enlightened activity." -- Shunryu Suzuki
[reply]
Re: Appending data to a file in a specific location
by gemoroy (Beadle) on May 01, 2009 at 17:18 UTC
    So you need defineв ifaces and there's ip's? 
    ...
while(/\*\*\*\() \*\*/g)
{
my $iface = $1;
if(/\G ip adress (\d+\.\d+\.\d+\.\d+/){print "iface $iface is definde 
+with $1"}
}
...

    [download]
    I could be wrong.
[reply]
[d/l]
Re: Appending data to a file in a specific location
by pileofrogs (Priest) on May 03, 2009 at 19:34 UTC

    Heh.. I was just about to say the same thing: Expect is good.

    Can you clarify your question? Are you asking how to talk to your Cisco device or how to edit a text file? Editing the file is easy. Talking to the Cisco device is less easy.

    --Pileofrogs

[reply]

      Hi,

      Thanks for the reply, the end goal is to apply the changes to the actual Cisco devices. But at the moment I have a list of devices that have the ip helper-address defined and I only want to touch these configs and not any others and I need to adjust quiet a few. So the first pahse is to add the extra 2 ip helper-address to the configs and then apply these to the devices. But I do not want to apply the changes after the config adjustement as we have a product to do this but the product is not flexiiable enough to make these types of changes as to match any interface that has the ip helper address defined, so I though PERL would be the right tool for that job.

      Hope that explains things

      Kind Regards

      James

[reply]

        Sorry, I still don't understand: Do you have text files on your desktop that need editing, or do you need to edit the files on the Cisco device?

        I had a system once where I needed to automatically make a change on a Cisco device during a failure state. I had a linux box attached to the Cisco device via serial cable. I used minicom to talk to the Cisco device. I wrote a perl script with expect that fired up minicom and talked to the Cisco. If it would be helpful, I could probably fish it out and you could take a look at it.

        -Pileofrogs

[reply]

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