I have been learning some network and system administration and encountered a puzzling problem.
SETUP:
I setup a small local offline network with a Windows Server 2019 and a Ubuntu server hosting gitea. In the Windows Server I have assigned a static IP of 169.254.0.2 and installed DNS and DHCP roles. In the Ubuntu server I have assigned a static IP of 169.254.0.3.
DNS has been configured with a primary zone funlab.abc. I created a single A record for gitea.funlab.abc. to point to 169.254.0.3. DHCP has been configured to lease addresses from 169.254.0.100 to 169.254.255.254. Subnet mask is 255.255.0.0.
PROBLEM:
With this setup, I successfully got client machines to connect to the local LAN network, transparently get a dynamic IP address, and access gitea.funlab.abc through the browser.
But in windows 10 client machines, I am unable to run ping gitea.funlab.abc in command prompt. I get an error message :
Ping request could not find host gitea.funlab.abc. Please check the name and try again
Git clone/push operations involving the URL gitea.funlab.abc also does not work.
However I can run ping -4 gitea.funlab.abc successfully. Git clone/push operations can also work if I replace the URL with the static IP. nslookup gitea.funlab.abc works correctly as well.
QUESTION:
Why is this happening? What did I misconfigure such that ping and git commands do not work?
Turns out ping and git commands works just fine when I change the IP address to 192.168.X.X. I guess windows treat the 169.254.X.X addresses differently.
I'm new to Amazon Web Service (AWS).
I already created a PostgreSQL from AWS RDS:
Endpoint: database-1.XXX.rds.amazonaws.com
Port: 5432
Public accessibility: Yes
Availablity zone: ap-northeast-1c
After that, I will push my application that using the database to AWS (maybe deploy to EKS).
However, I want to try testing the database server from my local computer first.
I haven't tried testing from my laptop PC at home yet, but I think it will connect OK because my laptop PC is not using the HTTP proxy to connect to the network.
The problem is that I want to try testing from my company PC, which needs setup the HTTP proxy to connect to the internet. The PC spec:
Windows 10
Installed PostgreSQL 10
Firstly, I tried using psql command-line:
psql -h database-1.XXXX.rds.amazonaws.com -U postgre
> Unknown host
set http_proxy=http://user:password#my_company_proxy:3128
set https_proxy=http://user:password#my_company_proxy:3128
psql -h database-1.XXXX.rds.amazonaws.com -U postgre
> Unknown host
set http_proxy=http://my_second_company_proxy:3128
set https_proxy=http://my_second_company_proxy:3128
psql -h database-1.XXXX.rds.amazonaws.com -U postgre
> Unknown host
Then, I tried using the pgAdmin tool.
As from the internet post, it said that we can use "SSH Tunnel" for inputing proxy:
However, the error message will be shown:
So, anyone can help suggest if we can connect to the public PostgreSQL server through HTTP proxy?
I think problem is Postgres uses plain TCP/IP protocol and you are trying to use HTTP proxy. Also you're trying to create SSH tunnel against your HTTP proxy server which won't work.
So I'd suggest following solutions:
Use TCP proxy instead of HTTP proxy
Create an EC2 or any instance that has SSH access from your company network and has access to public internet. So that you can create SSH tunnel through that instance to achieve your goal.
NOTE: Make sure you PostgreSQL is accessible from public internet (although this is usually bad idea, but it's out of scope this question) sometimes security group configs prevent it to connect from public internet.
Just add all ports(5432,3128...) in the Security Group from your RDS and specify your IP. Don't forget "/32"
Let me add that "unknown host" is usually an indication that you're not resolving the DNS hostname. Also, your HTTP proxy should not interfere with connections to databases since they aren't on port 80 or 443. A couple of things you can try (assuming you're on windows) sub in your actual url:
nslookup database-1.XXXX.rds.amazonaws.com
telnet database-1.XXXX.rds.amazonaws.com 5432
You should also check the security group that is attached to your RDS and make sure you've opened up the ip address that you're originating from on port TCP/5432.
Lastly check that your VPC has DNS and Hostnames enabled. https://docs.aws.amazon.com/vpc/latest/userguide/vpc-dns.html#vpc-dns-updating
My lab runs RStudio on a server. A couple weeks ago, from my cousin's house, I successfully ssh'd into the server and pulled up the server-side RStudio through my local Firefox browser. Now when I try to access the server RStudio from home (via my own router), it doesn't work. I need help troubleshooting, and I'm guessing it's some problem on the router. I'm running Mac OSX 10.6.8. No idea what the university server's running, but I don't think it's a server-side problem.
Here's how it worked the first time I did it, at my cousin's house: first, I VPN into the university network; then I call SSH with port forwarding; then I open a Firefox browser, connect to my localhost port, and it opens up RStudio on the server side which I can access through my local browser window.
Here's the problem I'm having right now when I try to log-in from my home network:
I can make the VPN connection successfully. I can also set up SSH successfully with this command:
ssh -v -L 8783:localhost:8783 myacct#server.com
Here are the last several lines of the verbose output from the successful ssh command:
debug1: Authentication succeeded (password).
debug1: Local connections to LOCALHOST:8783 forwarded to remote address localhost:8783
debug1: Local forwarding listening on 127.0.0.1 port 8783.
debug1: channel 0: new [port listener]
debug1: Local forwarding listening on ::1 port 8783.
debug1: channel 1: new [port listener]
debug1: channel 2: new [client-session]
debug1: Entering interactive session.
Last login: Mon Sep 2 04:02:40 2013 from vpnipaddress
So I think I'm still succeeding at the VPN and SSH stage (though I don't know why it says my last login was Sep 2 when I've logged in a few times since then).
Next, I open Firefox, and I type localhost:8783, and instead of getting an RStudio server app through my browser window, I get the following errors:
In the Firefox browser window, it says: Server not found, Firefox can't find the server at www.localhost.com, Check the address for typing errors etc.
In the terminal window, it says:
debug1: Connection to port 8783 forwarding to localhost port 8783 requested.
debug1: channel 3: new [direct-tcpip]
channel 3: open failed: connect failed: Connection refused
debug1: channel 3: free: direct-tcpip: listening port 8783 for localhost port 8783, connect from 127.0.0.1 port 50420, nchannels 4
I'm not sure what I've got wrong. I haven't changed anything on my laptop since my last successful connection. I'm on my own router (instead of my cousin's), so maybe I need to mess with the firewall? I already allowed ports 22 and 8783 to come through the firewall to my laptop (I'm not even sure I needed to do that though). Help?
ssh -v -L 8783:localhost:8783 myacct#server.com
...
channel 3: open failed: connect failed: Connection refused
When you connect to port 8783 on your local system, that connection is tunneled through your ssh link to the ssh server on server.com. From there, the ssh server makes TCP connection to localhost port 8783 and relays data between the tunneled connection and the connection to target of the tunnel.
The "connection refused" error is coming from the ssh server on server.com when it tries to make the TCP connection to the target of the tunnel. "Connection refused" means that a connection attempt was rejected. The simplest explanation for the rejection is that, on server.com, there's nothing listening for connections on localhost port 8783. In other words, the server software that you were trying to tunnel to isn't running, or else it is running but it's not listening on that port.
Posting this to help someone.
Symptom:
channel 2: open failed: connect failed: Connection refused
debug1: channel 2: free: direct-tcpip:
listening port 8890 for 169.254.76.1 port 8890,
connect from ::1 port 52337 to ::1 port 8890, nchannels 8
My scenario; i had to use the remote server as a bastion host to connect elsewhere. Final Destination/Target: 169.254.76.1, port 8890. Through intermediary server with public ip: ec2-54-162-180-7.compute-1.amazonaws.com
SSH local port forwarding command:
ssh -i ~/keys/dev.tst -vnNT -L :8890:169.254.76.1:8890
glue#ec2-54-162-180-7.compute-1.amazonaws.com
What the problem was:
There was no service bound on port 8890 in the target host. i had forgotten to start the service.
How did i trouble shoot:
SSH into bastion host and then do curl.
Hope this helps.
Note: localhost is the hostname for an address using the local (loopback) network interface, and 127.0.0.1 is its IP in the IPv4 network standard (it's ::1 in IPv6). 0.0.0.0 is the IPv4 standard "current network" IP address.
I experienced this error with a Docker setup. I had a Docker container running on an external server, and I'd (correctly) mapped its ports out as 127.0.0.1:9232:9232. By port-forwarding ssh remote -L 9232:127.0.0.1:9232, I'd expected to be able to communicate with the remote server's port 9232 as if it were my own local port.
It turned out that the Docker container was internally running its process on 127.0.0.1:9232 rather than 0.0.0.0:9232, and so even though I'd specified the container's port-mappings correctly, they weren't on the correct interface for being mapped out.
In my case, it worked after running the vncserver on linux.
Entered this on linux command line : sudo ssh -L 5901:localhost:5901 -i <ssh_private_key> <username>#<public-IP-address>
Type there vncserver
Go to VncViewer application and connect using localhost:5901
I used to meet the similar problem because 'localhost' was not available on server when it restarted network service, e.g. 'ifdown -a' but followed by only 'ifup -eo1'. Besides server is not listening to the port, you can also check 'localhost' is available or not.
ps: Post it just hope someone who has the similar problem may benefit.
I had this problem when I wanted to make a vnc connection via a tunnel.
But the vncserver was not running.
I solved it by opening the channel on the remote machine with vncserver :3.
In my case, it worked after checking the correct IP address of the user credentials
previously I was using the wrong IP of the server
ssh -NfL 127.0.0.1:8084:127.0.0.1:8888 user#ip_address_of_server
after correcting it, works fine.
Encountered with the same error.
In my case, I found the problem was in the config file of jupyter.
Let's say there are 3 computers named A, B, and C, and A can access B but can't access C; B can access C.
To access jupyter-notebook service of C from A, first I established ssh tunnel from A to C through B, then I access jupyter-notebook by typing localhost:port_number, then I got the error.
Finally the problem was solved by writing the "c.NotebookApp.ip = '0.0.0.0'" in jupyter-notebook's config file, where '0.0.0.0' allows the access of other IPs.
Hope someone in a similar situation may benefit.
I had the same error when I was trying to tunnel my mlflow ui over ssh to view remotely. As mentioned in the first answer, the error arises because nothing on the server is listening for the port. This, for me, is because I forgot to start the mlflow app on my remote machine! So in general – make sure the app you're trying to access remotely is running.
Just replace localhost with 127.0.0.1.
(The answer is based on answers of other people on this page.)
This means the remote vm is not listening to current port i solved this by adding the port in the vm server
I am trying to run putty on Windows 7.
I need to run some SSH commands to upgrade Magento. Every time putty gives me this fatal error:
network error: connection refused
I have even tried to use it through winSCP. Note that putty is running fine on my client's side, but for me it's giving me that error every time.
I tried using port 22, 23 and a few others without success. I have also tried with Windows Firewall both enabled and disabled.
Thank you.
Install open-ssh or ssh in target Linux machine solved my problem .
Use below commands:
sudo apt install ssh
sudo systemctl status ssh
sudo systemctl enable ssh
The following are the list of possibilities of this error:
1) Common cause is - Your IP is blocked or not whitelisted in the server which can be done by editing the file at /etc/csf/csf.conf
2) Disable the windows firewall settings and check..
The above two things should work in most of the cases
3) This is very unusual and when the above two options fails it is very difficult to find the solution
In this case the traceroute to the server host or IP works usually but putty fails
port 22 looks normal and working but connection fails and restarting SSH (service ssh restart) also does not work
reboot or restart the server but still fails
Adding IP in firewalls or whitelisting the local IP may not workout
This case generally happens when the server is migrated or new server. IP of the old server might be whitelisted locally, but don't have port 22 open, or some other local filtering is occurring for this new IP but not the old server IP..
In this case you need to change the port to some 522 or 530 some unusual port will help in sorting it out.. The same port you have to use for the SFTP connection also .. where as FTP connections works normally..
or you have to whitelist the IP locally or open the TCP in and out to port 22 if you want to use the port 22..
A service, for example an FTP server, only accepts connections from a specific network, where all users will have the same external IP-adress.
I want to connect to this service, but I'm currently not inside the allowed network.
I have ssh access to a server inside the network.
How do I use ssh to tunnel a certain port from my local machine, through a machine on the internal network, to the final service, so that any client opening the correct port won't notice any difference?
You can create a SSH tunnel to your specific network using the following command.
For instance, let's say you want to reach a web service on computer "mywebserver" (port 80).
Under Linux or BSD, using OpenSSH, you can use the following commandline:
ssh -f mysshserver -L 1234:mywebserver:80 -N
Under Windows, you can use MobaXterm which includes a simple graphical ssh tunnel builder
This will open a SSH tunnel between local port 1234 and remote webserver on port 80. You can then open your web browser and connect directly to your web server by typing "http://localhost:1234" in the address bar.