I recently got to know about DNS (Domain Name System Or Domain Name Server) and how it works. I want to know - can I access to a website by using its IP address and how?
-ThankYou
TL;DR: It depends how the server is configured but probably not and I would not rely on it.
This is because the website you are trying to access is likely behind a reverse proxy or load balancer. The load balancer acts like a railroad switch depending on the hostname you use to connect to it.
For simplicity, imagine that google.com and mail.google.com are on the same server with the same IP: 192.168.1.1.
If you were to try to connect directly to http://192.168.1.1/, how would the web server know which service you wanted? It wouldn't. In fact there are companies who's business is based solely around load balancing other companies' servers.
When you connect to a host with your browser, for example: https://www.google.com, your browser sends a special HOST=www.google.com header behind the scenes. The load balancer processes this header and routes the request to the correct server (which may be on a completely different server, network, etc).
Digital Ocean has a great tutorial on how to configure a basic virtual host for nginx. This demonstrates the basics of what a multi-host configuration might look like.
If you don't want to mess with DNS servers, you could set up a local lab environment on your desktop simply by modifying your hosts file. You can google where your operating systems hosts file is located.
If you have access to cURL, you can test the results like so:
# if you've configured a virtual host for mysite01.local on port 80
curl --verbose --header 'Host: mysite01.local' 'http://127.0.0.1'
# if you've configured a virtual host for mysite02.local on port 80
curl --verbose --header 'Host: mysite02.local' 'http://127.0.0.1'
# depending on your configuration this may return a 404 or point to one of your previous sites
curl --verbose 'http://127.0.0.1'
Yes, you can access any domain using IP address. Domain is just a name of website, IP address is the address of the page/website.
You can always ping website using command prompt:
ping www.google.com
You get one ip address which in this case is 216.58.197.78. Now when you hit the ip address in browser you will be redirected to google.com.
You can think of DNS (Domain Name System) as a table which provides mapping between IP address(216.58.197.78) and domain name(www.google.com)
Related
Could deploy Bosh and small footprint tanzu application service(tas) in Azure, without using the domains.All Vms are running.Can i access the ccapi and apps manager with the IP address instead of the api.SYSTEMDOMAIN?
The short answer is no. You really, really want to have DNS set up properly.
Here's the long answer that is more nuanced.
All requests to your foundation go through the Gorouter. Gorouter will take the incoming request, look at the Host header and use that to determine where to send the request. This happens the same for system services like CAPI and UAA as it does for apps you deploy to the foundation.
DNS is a requirement because of the Host header. A browser trying to access CAPI or an application on your foundation is going to set the Host header based on the DNS entry you type into your browser's address bar. The cf CLI is going to do the same thing.
There are some ways to work around this:
If you are strictly using a client like curl where you can set the Host header to arbitrary values. In that way, you could set the host header to api.system_domain and at the same time connect to the IP address of your foundation. That's not a very elegant way to use CF though.
You can manually set entries in your /etc/hosts` (or similar on Windows). This is basically a way to override DNS resolution and supply your own custom IP.
You would need to do this for uaa.system_domain, login.system_domain, api.system_domain and any host names you want to use for apps deployed to your foundation, like my-super-cool-app.apps_domain. These should all point to the IP of the load balancer that's in front of your pool of Gorouters.
If you add enough entries into /etc/hosts you can make the cf CLI work. I have done this on occasion to bypass the load balancer layer for troubleshooting purposes.
Where this won't work is on systems where you can't edit /etc/hosts, like customers or external users of software running on your foundation or if you're trying to deploy apps on your foundation that talk to each other using routes on CF (because you can't edit /etc/hosts in the container). Like if you have app-a.apps_domain and app-b.apps_domain and app-a needs to talk to app-b. That won't work because you have no DNS resolution for apps_domain.
You can probably make app-to-app communication work if you are able to use container-to-container networking and the apps.internal domain though. The resolution for that domain is provided by Bosh DNS. You have to be aware of this difference though when deploying your apps and map routes on the apps.internal domain, as well as setting network policy to allow traffic to flow between the two.
Anyway, there might be other hiccups. This is just off the top of my head. You can see it's a lot better if you can set up DNS.
The most easy way to achieve a portable solution is a service like xip.io that will work out of the box. I have setup and run a lot of PoCs that way, when wildcard DNS was something that enterprise IT was still oblivious about.
It works like this (excerpt from their site):
What is xip.io?
xip.io is a magic domain name that provides wildcard DNS
for any IP address. Say your LAN IP address is 10.0.0.1.
Using xip.io,
10.0.0.1.xip.io resolves to 10.0.0.1
www.10.0.0.1.xip.io resolves to 10.0.0.1
mysite.10.0.0.1.xip.io resolves to 10.0.0.1
foo.bar.10.0.0.1.xip.io resolves to 10.0.0.1
...and so on. You can use these domains to access virtual
hosts on your development web server from devices on your
local network, like iPads, iPhones, and other computers.
No configuration required!
Well i have a machine and i want to do a very simple thing, on this machine i have 3 DNS records,
for example 111.111.111.111 is the ip of the machine itself
test1.whatever.net - 111.111.111.111
test2.whatever.net - 111.111.111.111
test3.whatever.net - 111.111.111.111
We would like the traffic coming through each DNS record to be
handled by each corresponding service.
Create 3 very simple scripts that act as a website using any language
or platform (suggested NodeJs), that echo the name of the service
when calling the DNS record (e.g. "service1", "service2" and
"service3").
how do i do that?
All of the services must run on port 80
The machine is AWS Linux 2
What http server are you using?
Usually you can solve this issue with creating virtual hosts. In Apache it would look like this: https://httpd.apache.org/docs/2.4/vhosts/examples.html
There you can define, based on the DNS request, which folder the webserver should use to present the client.
Another option, but this might be more complex, when you setup an nginx proxy. https://docs.nginx.com/nginx/admin-guide/web-server/reverse-proxy/
I have tried to send a DNS packet to get an IP of some web-site.
In some cases, like google, the IP was right and when i typed it in the url line it sent me to google.
But in other cases (for example : stackoverflow.com) its gave me an IP that didin't linked to the web-site.
To be sure that my packet is right, i tried to do Nslookap in the command line, and the result was the same.
So i cant find the right IP adress of a web-site.
There is the message that appear when I'm trying to enter stakoverflow
Fastly error: unknown domain: 151.101.65.69.
Please check that this domain has been added to a service.
You (generally speaking) can not open the website just by entering the IP address in your browser's address bar because web servers (and possibly many other network components that are between you and the web server) often do not host only one web site on that IP address so they rely on exact domain name typed in address bar to serve the right content.
I think, it's caused by yours internet restriction. Try to contact your ISP (your internet provider) about this problem. He will probably know more about cause of this problem.
Short answer: you need a host header.
Long answer: Since HTTP/1.1 introduced in 1997 (and then updated in 1999 and in 2014), the request needs a host header. That allows the web server to route a request to a corresponding server configuration, a virtual server in Apache speak. Some servers don't have this configured and is allowing requests to any host to be served from the same web server configuration.
HTTP/1.1 also allowed multi-tenant proxies, as Fastly, to exist in the Internet. Fastly is a CDN - content delivery network - that allows to cache websites content on closer to users and deliver it locally (faster than from a cloud or a colo, thus the name).
When you're not specifying the domain for the request, it looks like your client (or a library) is using the IP address as the host header. That's why the response from Fastly talks about domain: unknown domain: 151.101.65.69.
While Fastly do support service pinning to a dedicated IP address, which would have worked for your request - it doesn't look like stackoverflow is using the feature as they might not need it.
My Oracle 11.2 database schema has a scheduled job that queries a webpage on my website every few minutes. The database and web servers are two physical Linux machines that sit next to each other and have local IP addresses 192.168.0.11 (database) and 192.168.0.12 (web server). There is a RJ-45 cable cross-connect that directly links the two servers on the same subnet.
If I enter the web address http://xxx.xxx.xxx.xxx/path/to/webpage where xxx.xxx.xxx.xxx is the external IP address, things work fine. Things also work well if I replace xxx.xxx.xxx.xxx with www.mydomain.com.
However, I'm thinking it should be much more efficient if I could re-write xxx.xxx.xxx.xxx as 192.168.0.12 thinking that this would avoid having the request go out on the internet and come back, but rather stay on the same subnet to get to the webpage (thus saving time and resources).
req := UTL_HTTP.BEGIN_REQUEST('http://192.168.0.12/path/to/webpage');
When I try that, I get a 404 error, which makes me think it didn't get to the right webpage.
Can I keep the query on the same subnet by modifying the hosts file or some other way?
My current hosts file already contains an alias for the email server, that is:
192.168.0.12 mail.mydomain.com
If I also include the web address such as
192.168.0.12 mail.mydomain.com www.mydomain.com
would that keep the database on the same subnet when accessing the website? Or will it still leave the subnet to get there? Also, will it confuse things now that I've got two aliases (e.g. one for the database to send emails and one for the database to access webpages)?
I am not sure I would add "192.169.0.12 mail.mydomain.com www.mydomain.com" if that is not the proper IP for the host. That might only make things more confusing.
Assuming that you can ping 192.168.0.12 from the DB server, make sure that your Web Server is listening on the 192.168.0.12 address as well. It could be listening only on the external IP address, in which case, it will return HTTP 404 to every request on the 192.168.0.12 IP/interface.
On Apache, the httpd.conf file would have
listen xxx.xxx.xxx.xxx:80
which would make it listen on the external IP only.
Please note that if the purpose of your HTTP requests is to test the web server availability, you may be better of leaving things as they are. The external test is much more compreheensive than a local one could ever be.
When using host headers to host multiple websites on the same IP address in IIS, is there any way of accessing that website from a browser running on the local machine?
This is normally required when a given web component only allows configuration from the local machine. It's also useful when things like ASP.Net's built in error handling isn't working and you can only view the error in the browser but don't want to allow remote users to see it.
This has baffled me for a while and everytime I come across it I end up giving up in frustration and reconfigure stuff so I can accomplish such tasks remotely.
Added: #Ishmaeel - modifying hosts doesn't seem to help - you either get a 400 error (if all websites have host headers) or whichever site is configured without a host header.
Just an idea: Mapping the hostname to 127.0.0.1 in the hosts ($WINDOWS$\system32\drivers\etc) file may help. This way you should be able to pull up the local IIS site by typing the hostname as if it's a remote server
Maybe I am not understanding the question, but what's wrong with just typing in the URL for the website? If it's the matter of domain name resolution, you can point to the right DNS or put it in hosts file.
eed3si9n -- if you are trying to access a url locally and you use host headers you cant just type in the url: for example you have 2 websites (website1.com website2.com) on 1 server using host headers. the local ip of the web server is 192.168.1.50 --> if you type in 192.168.1.50 you will get a 'page cannot found'. if you put in the url website1.com or website2.com you will be accessing the sites from the outside (not locally).
so the problem is how to access the sites locally not from the outside -- for example i need this ability so that i can access locally as the test sites are only available locally. not from the outside...
You can try telnetting to the server.
$ telnet localhost 80
(type these lines manually)
GET / HTTP/1.1
Host: www.example.com
(exchange www.example.com for the host name your server is mapped to)
I would assume the only way you can do this is assigning a custom port to the specific website you want to monitor and just access it as "localhost:CustomPort".