Mikrotik Scripting: Resolve Domain to IPv6 Address

Hello Mikrotik users.

Unfortunately Mikrotik does not provide an explicit function for resolving DNS names to IPv6 addresses. The :resolve function only returns a single IPv4 address when both v4 and v6 addresses exist for this domain, which you can see with this terminal command

:put [:resolve dns.google.com]

But if you need to get the IPv6 counterpart you can do this with a trick by using a temporary IPv6 firewall address list.
You could have used web services and external APIs and make an http call using /tool fetch on the device, but I wanted solve this without using external services.

As a result, I wrote an easy to use global function for the problem:

Function "$resolveipv6"

# define global function to resolve IPv6 DNS Names to IPs
:global resolveipv6 do={
    :local result [:toarray ""]    
    :local maxwait 5
    :local cnt 0
    :local listname "tmp-resolve$cnt"
    /ipv6 firewall address-list {
        :do {
            :while ([:len [find list=$listname]] > 0) do={
                :set cnt ($cnt + 1)
                :set listname "tmp-resolve$cnt"
            }
            :set cnt 0
            add list=$listname address=$1
            :while ([find list=$listname && dynamic] = "" && $cnt < $maxwait) do={:delay 1;:set cnt ($cnt +1)}
            :foreach i in=[find list=$listname && dynamic] do={
                 :local rawip [get $i address]
                 :set result ($result, [:pick $rawip 0 [:find $rawip "/"]])
            }
            remove [find list=$listname && !dynamic]
        }
     }
    :return $result
}

The function, once called in a script, can be used like this in scripts or on the console:

Output of addresses on the console (returns an array if there are multiple addresses)

:put [$resolveipv6 "dns.google.com"]

Results in an array of two addresses

2001:4860:4860::8844;2001:4860:4860::8888

Store result in a variable and retrieve individual addresses via index

:local myvar [$resolveipv6 "dns.google.com"]
# get first address of result
:put [:pick $myvar 0]
# get second address of result
:put [:pick $myvar 1]

Important note: If you put the function in a startup script it will be available in all scripts and the console as soon as you declare it once by this call:

:global resolveipv6

Maybe this is helpful for someone until Mikrotik itself provides an IPv6 capable resolve variant.

Greetings and all the best for the new year.
@colinardo

Please also mark the comments that contributed to the solution of the article

Content-Key: 5151910821

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Printed on: June 4, 2023 at 20:06 o'clock

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