Hey guys!
This is my first thread so feeling really excited!!

So my question is i have a dynamic external ip and i'm just tryin to access my local server on my laptop from internet via my external ip...
But i'm not able to port forwrd it.

I even tried:

iptables -t nat -A PREROUTING -d 192.168.1.1 -j DNAT --to-destination 192.168.1.x on my router via telnet...

I make sure that i do not reboot my router(since its dynamic and it will change)

Any suggestions

If I understand you right, you're attempting to connect to your server through your laptop via telnet?

This is a very very very bad idea. telnet is not secure.

Use ssh.

To port forward a remote port to a local port:

The -N doesn't grab a shell or send a command (good for forwarding ports)
-R indicates a reverse port (i.e. remote to local port instead of local to remote)

You will need port 22 open on the server if connecting via external ip.
Note that the other ports will not need to be open. If you bind 9876 on the remote host to 7000 on the local ip, you still only need port 22 open.
It is a wise idea to use public key auth - especially on any external network.

You can use Match Statements to fine tune what people can do who connect. You can configure it in /etc/ssh/sshd_config

Ensure AllowTcpForwarding is set to yes to enable port forwarding
I'm pretty sure it defaults to yes if not specified though.

Welcome to LinuxQuestions.

What is the make/model of your router? Typically 192.168.1.1 would be the LAN address of the router and not its external address. How do you want to access the server? What do you want to accomplish? i.e. remote desktop etc.

My understanding is the OP is using telnet to access the router.

first upon u need a static ip from ISP
using dynamic external ip u cannot connect to ur server.
Else u can use dyndns or noip subscription to acheive ur goal. Also need to forward appropriate port in the router/modem.