How is it possible to access an internal resource (email server / FTP server) using its external IP address but from within the network ?
The situation is that a number of users have laptops and work out of the office several days per week. I don't want them to have to change the connection details from 217.x.x.x to 10.0.0.x every time they come into the office, then back again when they leave.
I have external access working, so they can connect using the 217.x.x.x IP when on the road, but it doesn't work when they are in the office.
We have a router providing NAT access to the net and different servers for FTP, email etc.
This is what DNS is for - your external DNS provides the 217.x.x.x address for the names, while your internal DNS returns the 10.0.0.x IP address. Clients access resources by hostname, not IP address, and it's done.
Unless you have filters forbidding access to the external NAT'ed address from internal clients, I do not see why it should not work.
Related
I am developing a custom Alexa Skill and have a requirement where I want Alexa to access REST APIs that are hosted locally on http://localhost:8080? Any idea how to do this?
Thanks!
If you really want to do this, and I’m assuming you are hosting the skill on AWS Lambda, it would involve quite a bit of work.
Your local endpoints need to be accessible from outside of your network, which requires port forwarding in your router to your machine where the endpoints are hosted. This needs to be configured in your router.
An easier way is to deploy your project containing the API to something like Heroku, which can be done easily. They give you a domain and make the endpoints accessible to Lambda. This should be possible within their free tier.
Here' a link to a pretty good article about how IP addresses work.
Allowing a device sitting on your local network (eg. a laptop computer or Raspberry Pi connected to your wifi) to be accessed from outside your local network (eg. from a service running on AWS) will involve mapping 2 separate IP addresses:
The IP address assigned to your router (your public IP)
The private IP addresses assigned by your router to your devices (laptop, iPhone, RPi, etc).
You have a couple options for allowing your router's IP (#1) to be accessible from outside your local network:
a. Pay your internet provider to provide you with a static IP address
b. Use a dynamic DNS service such as DuckDNS or No-IP.
Once you have a fixed public IP that can be used to access your router, you will then need to map a port on your router (#1) to the device IP on your local network (#2). This is usually referred to as "port forwarding". Most routers will support configuring this. In effect, your tell your router "when you get a message to : pass it to my laptop :"
Your local private IP address will typically have an IP value like 192.168.0.23 (where the 23 can be anything from 1 to 254).
An outside IP will start with something other than 192. Refer to the first link above regarding IP ranges.
You can google "port forwarding" and "public IP" for more info on how IP addresses and port forwarding work, but hopefully this will help get you started. It may seem a bit complicated at first, but if I can understand it, then anyone can :-)
I need to run an XMPP server for IM with end-to-end encryption and voice calling. I'm trying to set up Prosody, but is it possible to run an XMPP server without a domain name? Without own DNS server and VPN network between clients?
Short Answer: Yes.
You can still configure a XMPP domain for your server. According to the standard, it doesn't has to be an DNS Name or IP address. Something like myserver is fine. Quoting RFC 7622 § 3.2:
The domainpart for every XMPP service MUST be a fully qualified domain
name (FQDN), an IPv4 address, an IPv6 address, or an unqualified
hostname (i.e., a text label that is resolvable on a local network).
But if you don't have a DNS name, then clients won't know automatically how to reach your server. Which means you have to configure the IP address and the port in every client.
You can use an IP address instead of a domain name, but if that address will be changing on a regular basis, you'll probably need modifications to standard XMPP servers and clients, as they'll not be expecting that.
I went through many Prosody tutorials and I think it is not possible to set up server based only on IP address and using SSL. I even have not found how to configure Prosody on local network with SSL and resolvable name like raspberry.local. My client always gave server not found, or incorrect communication.
So I am kind of new to networking and I'm just interested in the client/server architecture. Let's say you developed a program and the client version ran on a computer and the server version on the server(obviously). In order for the client to connect to the server, it would have to know the ip address of the server (and the port attached so it can be routed to the correct computer/program). Does that mean that the server's ip address can not change? Would you have to specifically tell your ISP to keep the ip address static? Because if both the client and server ip addresses change, then they would have no way to connect and the program wouldn't work... in other words there has to be one constant. When you sign up for a VPS do they give you a static ip address you can bind to from the client version? Thanks!
In order for the client to connect to the server, it would have to know the ip address of the server (and the port attached so it can be routed to the correct computer/program).
Correct.
Does that mean that the server's ip address can not change?
No. In fact, IPs can change at any time. Most servers that are exposed to the public Internet have a static domain name registered in the Internet's DNS system. A client asks DNS to resolve the desired domain name to its current IP address, and then the client can connect to it. But even in private LANs, most routers act as a local DNS server, allowing machines on the same network to discover each other's IP by machine name.
The OS typically handles DNS for you. A client can simply call gethostbyname() or prefferably getaddrinfo(), and the OS will perform DNS queries as needed on the client's behalf and return back the reported IP(s).
Would you have to specifically tell your ISP to keep the ip address static?
You can, but that usually costs extra. And it is not necessary if your server is registered in DNS. And there are free/cheap DNS systems that work with servers that do not have a static IP.
Because if both the client and server ip addresses change, then they would have no way to connect and the program wouldn't work...
That is where DNS comes into play.
in other words there has to be one constant.
A registered domain name that can be resolved by DNS.
When you sign up for a VPS do they give you a static ip address you can bind to from the client version?
It depends on the VPS service, but a more likely scenario would be you are assigned a static sub-domain within the VPS service's main domain. For example, myserver.thevps.com. Or, if you buy your own domain (which can be done very cheaply from any number of providers), you can usually link it to the DNS server operated by your VPS service.
My internet connection has a dynamic IP adress which keeps changing every time the modem is restarted, so I have a hard time configuring the Authorized Networks in Access Control.
This is explained at https://cloud.google.com/sql/docs/access-control#dynamicIP .
Your options are, and I quote:
Use a proxy service so that your application appears to come from only one IP address. Add this address to the authorized networks that can connect to the instance.
Use a CIDR range that covers all of the IP addresses from which your service might connect.
Use the CIDR range 0.0.0.0/0, which allows all external IP addresses to connect.
The third and last option, despite its attractive simplicity has implications that may make it undesirable -- read the docs I'm pointing to.
I need a IM client that support yahoo and allow user to set yahoo IM server address.
Yahoo IM servers names (scs.msg.yahoo.com, scsa.msg.yahoo.com, scsb.msg.yahoo.com, scsc.msg.yahoo.com) are not accesible through my company LAN, so I should use IP addresses of their servers.
We can find ip of a domain name by simply pinging that domain name.
My problem was related to another network issue (port 443 was blocked) but initially I supposed that it relates to server ip address.