Network Management

Running and Startup config comparisons show a difference where there are none

Comparison of startup and running configuration highlights differences yet configurations are identical.

First published date

10/15/2018 12:43 AM

Last published date

10/7/2022 7:03 PM

Overview

In the case of some devices, the startup and running configuration contains the same set of commands but when processed by the NCM comparison process they show there is a difference between the two (false-positive mismatch).

Product section

Network Configuration Manager

Cause

Some of the possibilities are:

  1. startup-config is in a different format than running-config, for example, XML vs TXT
  2. the comparison process is not ignoring hexadecimal data even after enabling "Ignoring hex data" criteria (the startup-config does not display the hex data but the running-config does), for example:
     
    • Standard hex keys are in blocks of 8 per line: 
      ^[ \t\r\n\v\f]*[A-Fa-f0-9][A-Fa-f0-9][A-Fa-f0-9][A-Fa-f0-9][A-Fa-f0-9][A-Fa-f0-9][A-Fa-f0-9][A-Fa-f0-9]
    • Config file comparisons may not ignore the hex data, if you use shorter blocks, like the sample given below: 
      ^[ \t\r\n\v\f]*[A-Fa-f0-9][A-Fa-f0-9][A-Fa-f0-9][A-Fa-f0-9][A-Fa-f0-9]
    • The word quit at the end of the Hex data is not at the beginning of the line in the config. It can be random on the line but generally close.

Resolution

In the first case (CAUSE 1) there is no possible solution as the "files" are essentially different and there is no viable method to compare them. Generally, you shall always compare configs of the same type: startup vs startup, running vs running.

In the second case (CAUSE 2), if hex keys are not in blocks of 8, you need to modify the 'Ignore quit word line' criteria: 

from: ^[ \t\r\n\v\f]*quit[ \t\r\n\v\f]*

to: [ \t\r\n\v\f]*quit[ \t\r\n\v\f]*

  1. Log in to the Orion Web console 
  2. Click Settings > NCM Settings > Comparison Criteria 
  3. Select "Ignoring quit word line" and click Edit.
  4. Edit RegEx pattern screen appears as shown in the example below:
     
     
  5. Edit the RegEx pattern as highlighted in the above screen and click OK. 
  6. Verify by comparing two configs being displayed as different previously.
  7. If the above comparison is corrected, Download a new set of configs to NCM regardless of whether a change is detected or not.  This will update the charts on the web page. They will not be automatically reconciled by simply correcting the Comparison Criteria.