Example Usage: Build configuration diffs

Let’s suppose we need to find all serial interfaces in a certain address range and configure them for the MPLS LDP protocol. We will assume that all serial interfaces in 1.1.1.0/24 need to be configured with LDP.

Baseline Configuration

This tutorial will run all the queries against a sample configuration, which is shown below.

! Filename: /tftpboot/bucksnort.conf
!
policy-map QOS_1
 class GOLD
  priority percent 10
 class SILVER
  bandwidth 30
  random-detect
 class default
!
interface Ethernet0/0
 ip address 1.1.2.1 255.255.255.0
 no cdp enable
!
interface Serial1/0
 encapsulation ppp
 ip address 1.1.1.1 255.255.255.252
!
interface Serial1/1
 encapsulation ppp
 ip address 1.1.1.5 255.255.255.252
 service-policy output QOS_1
!
interface Serial1/2
 encapsulation hdlc
 ip address 1.1.1.9 255.255.255.252
!
class-map GOLD
 match access-group 102
class-map SILVER
 match protocol tcp
!
access-list 101 deny tcp any any eq 25 log
access-list 101 permit ip any any
!
access-list 102 permit tcp any host 1.5.2.12 eq 443
access-list 102 deny ip any any
!

Diff Script

The script below will build a list of serial interfaces, check to see whether they are in the correct address range. If so, the script will build a diff to enable LDP.

from ciscoconfparse import CiscoConfParse

# Parse the original configuration
parse = CiscoConfParse('/tftpboot/bucksnort.conf')

# Build a blank configuration for diffs
cfgdiffs = CiscoConfParse([])

# Iterate over :class:`~IOSCfgLine` objects
for intf in parse.find_objects("^interface Serial"):

   ## Search children of the interface for 1.1.1
   if (intf.re_search_children(r"ip\saddress\s1\.1\.1")):
      cfgdiffs.append_line("!")
      cfgdiffs.append_line(intf.text)  # Add the interface text
      cfgdiffs.append_line(" mpls ip")

Result:

>>> cfgdiffs.ioscfg
['interface Serial1/0', ' mpls ip', 'interface Serial1/1', ' mpls ip', 'interface Serial1/2', ' mpls ip']
>>> for line in cfgdiffs.ioscfg:
...     print(line)
...
!
interface Serial1/0
 mpls ip
!
interface Serial1/1
 mpls ip
!
interface Serial1/2
 mpls ip
>>>