There is some thing wrong with the script it giving me router internal ip not wan ip

Could you please post your script here so that we may take a look?

/system script
add name=Dynu
policy=read,write,test
source=":global ddnsuser mydynusuername
:global ddnspass "dynupassword"
:global theinterface "IN"
:global ddnshost "myhost.dynu.com"
:global ipddns [:resolve $ddnshost];
:global ipfresh [ /ip address get [/ip address find interface=$theinterface ] address ]
:if ([ :typeof $ipfresh ] = nil ) do={
:log info ("DynuDDNS: No IP address on $theinterface .")
} else={
:for i from=( [:len $ipfresh] - 1) to=0 do={
:if ( [:pick $ipfresh $i] = "/") do={
:set ipfresh [:pick $ipfresh 0 $i];
}
}
:if ($ipddns != $ipfresh) do={
:log info ("DynuDDNS: IP-Dynu = $ipddns")
:log info ("DynuDDNS: IP-Fresh = $ipfresh")
:log info "DynuDDNS: Update IP needed, Sending UPDATE...!"
:global str "/nic/update?hostname=$ddnshost&myip=$ipfresh"
/tool fetch address=api.dynu.com src-path=$str mode=http user=$ddnsuser password=$ddnspass dst-path=("/Dynu.".$ddnshost)
:delay 1
:global str [/file find name="Dynu.$ddnshost"];
/file remove $str
:global ipddns $ipfresh
:log info "DynuDDNS: IP updated to $ipfresh!"
} else={
:log info "DynuDDNS: dont need changes";
} }