I know about Network Address Translation and how it works by replacing the source IP address (which is private) by its own public IP while forwarding packets into the network.
But the routers that we buy for personal use at home (Wifi routers) to connect to the internet do have a NAT functionality?
Yes, they always have NAT functionality. It is for saving IP address and the safe of your devices connecting to Internet.
Related
Using a network tool in an android phone, I found the Local IP and External IP as:
I believe both are the Public IP.
Pls be kind and let me know, what is Local IP and External IP in this scenario?
Regards
TekQ
The Local IP is the address that your provider (Verizon, AT&T, Sprint, etc...) uses to identify you on their network. The External IP is the address that websites (google.com, facebook.com, etc...) use to identify and communicate with you.
There is a translation process, known as Network Address Translation (NAT), that converts Local IP addresses into External/Public IP addresses. The NAT service is controlled by your cell network provider.
More information can be found on Wikipedia's Network Address Translation page.
How do I get the internal IP address and port of the local machine in a cross-platform way? Not internal within the LAN, but the ISP, so that other users of the ISP can connect? Is connecting to a VPS with a public IP enough to get the external IP and port outside the ISP? How to get the ISP subnet mask to know when another internal IP is within the NAT?
edit: Probably don't need this. NAT punch through is enough. Am I right that router's don't have the same traversal rules as ISP's?
A NAT's public IP address is its external IP address. I don't understand what you mean by internal IP address. By internal address usually is meant a device's local address.
All the users of an ISP is in local LAN if the ISP has only one NAT under which all the private IP address is assigned. Some ISPs has nested NATs. In that case users under different NATs are in different network.
You can get your NAT's external IP:Port by sending a stun request to a stun server. From the server's reply you can get your NAT's external/public IP:Port. If the users of an ISP are not in local LAN but under different NATs then using their external IP:port they can communicate.
I have a network like that:
Internet <-> Modem <-> Router (broadcast wifi)
I'm using Windows. If I use command: ipconfig, I only know Modem's IP through info of Default Gateway.
So, how to know the Router's IP in this network.
Thanks.
If you want to know the external (from the Internet IP) you can browse to http://www.whatismyip.com/ and check it there.
Or
You can check it inside the router's configuration page. Unfortunately you can't simply know it by being a member of its network since this is a limitation of the NAT and the IP protocol.
If you wish to know the router's IP inside the internal network of the router .
when running ipconfig it should be the Default Gateway entry.
If you know your IP and you know your Netmask, then you can easy find out the subnet. The Router's IP is "always" the first avaible IP in the subnet. Thats the case for your private IP.
For the public IP you can try a service like this one.
I've some doubts about a VPN.
I've been given a Cisco VPN client to connect to the LAN of my society. I use this to connect to a local server. I don't understand how the VPN is working.
I'm at home now. In the VPN Client I see an IP. If I go to http://www.whatismyip.com/ I see another IP, which is the IP I've when I'm also without the VPN Client, while I expected to see the IP of the VPN Client. If I use $_SERVER['REMOTE_ADDR'] I see another (third!) IP, while I expected the IP I see in the VPN Client.
Can you clarify please?
I need this to know if I'm identifies always from the same IP from the local server.
If I'm not mistaken, this should be correct. Please correct me if I'm wrong.
By default you have 2 IP addresses.
Local IP: IP address used to identify yourself within your LAN.
Global IP: A public IP used to gain access to the internet. At home it will most likley be a public IP NATTED* by your ISP.
Because you're also using a VPN connection, you'll receive a third IP.
Local IP for VPN: IP address used to identify yourself on the other end of the VPN.
*NAT = Network Address Translation
Working on Cisco ASA 5510 device I tried to use the broadcast IP address of a Public Network for NAT Static configuration and IOS allowed me to do it, but from outside it didn't work. After a while I changed the broadcast IP to an usable IP and it started to work.
I understand that on a physical interface we can't configured a broadcast IP address, but for NAT we have to do it, otherwise we loose many Public IP addresses from networks with /29 prefix.
I understand you need to squeeze one more IP address for you to use, however most routers don't support forwarding broadcast traffic, for a simple fact, if that is allowed, anyone can send a ping to someone's broadcast address and every host in that subnet has to reply, that is not acceptable.
Other Internet routers may not tell that IP address is broadcast or not, but think about your ISP router for your access circuit, it has to know that IP address is a broadcast, it has to know your ip range in order to set it up. And when someone send you a ping, the router will say: hey, that is a broadcast address on my client's interface, first thing I know as a router, I must not forward a broadcast, thus drop it.
Hope it helps.