Calculator written in route-map

Job Snijders job at
Tue Apr 1 15:11:00 UTC 2014

Hi all,

Do you often find yourself in need of a simple calculator, and all you have
available to you is a Brocade or Cisco IOS router?  No longer will you
experience the horror and dread of mental arithmetics. The route-map calculator
is here!

Brocade   :
Cisco IOS :
            (file size ~ 12 megabyte)

In general I don't find route-maps useful to accomplish, well, anything.
However, this is a striking example of re-usable configuration that has
a measurable impact on daily operations! 

Calculations can be performed with integers between 1 and 256. The
answer will be presented as a rounded positive integer. In case the
calculation would result in a negative integer, larger than 2^16
(65536), an helpful error message is generated: 65000:7777. For
divisions and substractions the order of the BGP communities is
relevant, one must always place the operator first!

arithmetic operators:

  'add' operator community:        65000:1
  'multiply' operator community:   65000:2
  'substract' operator community:  65000:3
  'divide' operator community:     65000:4

example output:
  telnet at input-router#show ip bgp routes detail | i COMMUNITIES
              COMMUNITIES: 65000:2 0:63 0:113    ! calculate 63 * 113 
  telnet at input-router#

  telnet at calculator#show ip bgp routes detail | i COMMUNITIES
              COMMUNITIES: 0:7119                ! result: 7119
  telnet at calculator#

Super convenient right?!

WARNING: due to IOS/Ironware architecture this route-map consumes quite
some memory. Always test in a lab before deploying in production!

Kind regards,


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