In the state of Australia I currently live in, there are 2 major ISP’s – Internode and Adam Internet.
Being a typical nerd and living with other typical nerds we of course have 2 ADSL connections, 1 to each of these providers which are shared out amongst the house.

However each of these providers have what we call in Australia – “unmetered content” that is to say download traffic from these sources is not measured and removed from our download allowances (yes, we have limits on what we can download).

So anyway, I’ll make like a sharp stick and get to the point.

We wanted to make sure that free traffic from each ISP would always go via that ISP’s link to save us on downloads and each ISP offers a list of the free IP’s in a nice text format:

Internode – https://customer-webtools-api.internode.on.net/unmetered_ip_address_list.txt
Adam Internet – http://www.adam.com.au/unmetered/unmetered_ip_address_list.txt

Note: The Internode list is on a https only server and the mikrotik can only do a http fetch. So in my case, I’ve used a php file with a simple include function hosted on my own server and when I try to download that, it simply relays the latest copy of the Internode list.

Here’s the adam version of the scripts commented:
===
Script: fetch-adam-ips-list
===

#Fetch (download) adam address list from their webserver
#Log completion
#Delay for 4 seconds (in case download process gets stuck)
#Run the Address parsing script

/tool fetch address=www.adam.com.au host=www.adam.com.au mode=http src-path=unmetered/unmetered_ip_address_list.txt
:log info "Download Complete"
:delay 4
/system script run Add-Adam-Unmetered-IPs

===
Script: Add-Adam-Unmetered-IPs
===

#Log beginning of modification
#If the unmetered address list file size is larger than 0, begin
#Remove all previous entries
#Put the content of the txt file into the variable $content
#Get the total length of $content

:log info "Beginning Adam freee Address List Modification"
:if ( [/file get [/file find name=unmetered_ip_address_list.txt] size] > 0 ) do={
  /ip firewall address-list remove [/ip firewall address-list find list=Adam-Unmetered]
  :local content [/file get [/file find name=unmetered_ip_address_list.txt] contents] ;
  :local contentLen [ :len $content ] ;

#Set lineEnd to 0
#Set line to null
#Set lastEnd to 0

:local lineEnd 0
:local line ""
:local lastEnd 0  

#Beginning of do/while loop
#Set lineEnd to the first point in the line there's a newline char
#Set line to be whatever is between lastEnd and lineEnd
#Set lastEnd to be lineEnd + 1 (ready for new line)

  :do {
    :set lineEnd [:find $content "\n" $lastEnd ] ;
    :set line [:pick $content $lastEnd $lineEnd] ;
    :set lastEnd ( $lineEnd + 1 ) ;

#if the line is not empty (1st char is a newline) do the following
#if line is longer than 0 characters - add a new ip firewall address list entry with $line as the address
#End if segment
#End do segment - while $lineEnd is smaller than the total length of the list
#End if segment
#Log completion

    :if ( [:pick $line 0 1] != "\n" ) do={
      :if ( [:len $line ] > 0 ) do={ /ip firewall address-list add list=Adam-Unmetered address=$line }
    }
  } while ($lineEnd < $contentLen)
}
:log info "Adam free IP List Modification Complete"

You can then use this address list in your mangle rules, or alternatively modify this script to make it add static router etc.

The IP address list segment is very versatile and can be modified to suit a number of different cases
Previously I’ve used modified versions of this to:
a) scrape spam blacklists
b) add conficker domains to a blocklist
c) pull admin IP addresses from a server to add to an allow list.

Have fun and post back if you have another use for these!