Get my Router's IP


I need to get the DSL-Modem’s IP to use it in various curl commands.
By default its IP is given but user as admin can change this IP, so I must fetch it.
Well I could use DNS method to get it but I’d prefer to don’t rely on it

Among various method, I thought to “traceroute” towards a reference site (ISP’s site for example) because this gives the name and IP of the gateway (so the router) in first instance.
If I use “Traceroute” from “Network utilities” provided with OS X, it’s rather instantaneous, and returns the full nodes list

If I try to do it (using defaults parameters) via a command Shell

do shell script “traceroute” it’s just endless !! Must force to quit

To make it useful, I try only 3 hops (I can even make it faster by using -q and -w options)

do shell script "traceroute -m 3"

I retrieve only
1 /ModemName/ ( 0.859 ms
2 * * *
3 * * *

I can’t never get the second and third routing IP address.

My question is : what happens if, instead, there is a router between the DSL Modem-Router and the Mac?
can I expect to retrieve only the first node’s IP or at least the two LAN Router’s IP?

Another way to retrieve fast and accurately the Modem’s IP?