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 : calculator-route-map.brocade.txt Cisco IOS : calculator-route-map.ioscisco.txt (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 10.1.1.1 | i COMMUNITIES
            COMMUNITIES: 65000:2 0:63 0:113    ! calculate 63 * 113 
telnet at input-router#

telnet at calculator#show ip bgp routes detail 10.1.1.1 | 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!