Prevent blocking remote port when setting up a SSH tunnel/SSH port forwarding?
Assume I create an SSH tunnel to a remote computer with
ssh foobar@remcomp -L 20110:remcomp:110
then it seems to me that on the remote computer port 110 is blocked for other
clients. Is this true?
How can I prevent this exclusive locking?
email@example.com (Peter Insold) writes:
> Assume I create an SSH tunnel to a remote computer with
> ssh foobar@remcomp -L 20110:remcomp:110
> then it seems to me that on the remote computer port 110 is blocked for other
> clients. Is this true?
Dag-Erling Smørgrav - firstname.lastname@example.org...remote/reverse port forward, ssh client setting source IPs to what ssh server reports
Note: most of this post is based on OpenSSH
When I do a remote forward (port on server listens for incoming
traffic, traffic gets forwarded to port that is listening on client),
the source IPs of all the incoming connections in the server app on
the client machine are 127.0.0.1/localhost. Using "-v", I can see that
sshd passes the IP addresses of what computers connected to the sshd's
port that forwards to the client. The client does not use/set the
originating information when connect. RFC 4254 requires the server
send the originating IP across the wire to the client.
---------...I have a question about Remote port forwarding in SSH
Hi, I am trying do remote port forwarding in SSH and make the forwarded
port available over a network.
One machine, S, is behind a firewall and I can ssh out, but not ssh
in. I can connect using a VPN which only works with Windoze. The other
machine, H, is behind a different firewall, and it can SSH in or out.
So I what I do is connect to the machine S from the machine H and then
give the command:
user@S$ ssh -R22222:localhost:22 H
Then, on the machine H, I give the command
user@H$ ssh -p 22222 localhost
and I am connected. Using public key authentication, I don't need to ...What is the difference between local port forwarding (-L) and remote port forwarding (-R)
I need to do an SSH tunnel to encrypt the data sent between an agent
and a the server. I'm able to establish a tunnel but there's something
that I can't understand...
What is the difference between the bit -L and the bit -R. I've read
the man of SSH on Fedora. It's seems to be simple but in practice, I
Can somebody help me on this subject?
Thanks a lot!
> What is the difference between the bit -L and the bit -R.
-L forwards a port from the client to the server.
-R forwards a port from the server to the client.
To reply by email,...Question concerning remote port-forwarding with SSH
I have difficulties to find out when I should use SSH remote port-forwarding e.g.
ssh sshserver -R 7777:localhost:110
Notice the -R and instead of -L
This would cause a data traffic (with the syntax: in-port:machine:out-port):
MailClient(on remote):* -> 7777:SSHServer:* -> 22:SSHClient(on localhost):* -> 110:MailServer(on localhost)
Are the following statement correct:
- Use remote port-forwarding (-R) when the connection between SSH-Server
and ApplicationServer (e.g.MailServer) should be encrypted
- Use "normal" port-forwarding (-L) when the connection between App...ssh port forward
Im trying to set up ssh local port forward.
But I dont know the ports to connect to on the remote machine
Is it possible to setup forward for a range of ports?
You can specify multiple ports to forward on the command line, or
establish a VPN if you have the need for UDP. See:
for info on both types.
On 21 Nov 2006 15:57:54 -0800
> Im trying to set up ssh local port forward.
> But I dont know the ports to connect to on the remote ma...Port Forwarding and Multiple SSH Servers
Behind my firewall I have several SSH servers that I connect to with
ssh -p xx user@firewall_IP_address
and then the firewall forwards it to the correct server, generally
running some version of Linux. The problem is this error message:
@ WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED! @
IT IS POSSIBLE THAT SOMEONE IS DOING SOMETHING NASTY!
Someone could be eavesdropping on you right now (man-in-the-middle
It is also possible that the RSA h...remote host access on a remote forwarded port
I tried to connect my home lan to my office.
So I want to use VNC in order to forward only one port.
Because of the firewall of my office(I don't manage), I want to create a
tunnel by this way :
to be able to use VNC by this way :
I use port 443 to bypass the firewall of my office.
So I use the commands :
OFFICE: ssh -g -R 5900:VNCServer:5900 -p 443 HOME_FIREWALL
HOME: vncclient HOME_FIREWALL
But it looks like if the -g option doesn't work wit...port tunneling over ssh (not port-forwarding in the traditional sense)
Does anybody know of a way to do port forwarding over ssh not using the
standard ssh functionality, but rather by running a utility on the server
and using a special client that forwards data through the terminal session.
I think PPP and slirp would do the job, but I would prefer to have a
standalone client that exists solely to forward one (or several) ports,
rather than acting as my main network connection.
> Does anybody know of a way to do port forwarding over ssh not using the
> standard ssh functionality, but rather by running a utility on the server
> and using a spe...Ports for DB2 behind firewall / ssh port forward
I'd like to connect to a remote DB2 Database V 8.2 using the "DB2
Steuerzentrale" (I guess it's called something like "DB2 management console"
in the English version). Since the database host is behind a firewall I
tried to communicate through ssh port forwarding.
Therefore, I run:
ssh -L 6789:remotename:6789 -L 50000:remotename:50000 -L
50001:remotename:50001 -L 523:remotename:523 remotename
Though the ssh connection is established, my "DB2 Steuerzentrale" won't
connect to localhost successfully and shows an error num...To Port Forward or Not To Port Forward
System: DP MDD G4, OS 10.4.9
Inet connection: DSL with static i.p.,Broadcom Gateway to Linksys
WRT54G Wireless Router using DHCP, 1 computer connected via enet, 3
connected wirelessly, basic home use only
Wireless security is very basic: Unique router name and pw, SSID
disabled, and connections allowed by MAC addresses only, Linksys
firewall is enabled with all the other features set to their defaults,
Mac OS firewall is disabled
I recently purchased a Logitec QuickCam Pro 5000 webcam that works just
fine with iChat right out of the box. Learning how to use it I found
some Apple docs and ot...Warning: remote port forwarding failed for listen port 4043
I have a script that does a port forwarding for me:
ssh -n -R localhost:4043:localhost:22 remoteserver.example.com
The problem with this is that if port forwarding fails, ssh prints
Warning: remote port forwarding failed for listen port 4043
But it STAYS CONNECTED instead of properly failing with exit code.
So it is a MAJOR pain to detect this condition and kill ssh.
How can I change is so that, when report port forwarding cannot be
accomplished, ssh exits right away?
I think that it is a bug, period.
>>>>> "Ignoramus3694" == Ignoramus3694 <...Forward only some ports through ssh
Is it possible to forward only some ports (cvs and mysql for example)
through ssh using the authorized_keys.
...ssh port forwarding
I am trying to get access to a friends' computer via ssh. Unfortunately, his
computer is behind a router which doesn't support NAT (Network Adress
Translation). Consequently, I cannot connect directly on his computer using
a command like "ssh user@ip_adress" because his router is blocking me.
Then, I got the idea that perhaps if my friend would start a ssh connection
from HIS computer to MINE, and then somehow by tunneling I would be able to
get access to his computer. But after having read the manpages of ssh and
something on the internet, I must state that I do n...ssh port forwarding
Please, explain me where I'm wrong.
I have two machines with linux and FreeBSD and I desire to have a
secure tunel for HTTP between them. So I make it in the following way:
linux@lunc:~$ ssh -2 -L 1234:localhost:6661 lunc@freebsd
and afer that I tried to make following HTTP request
"http://localhost:1234/" on my linux box by Firefox browser. However, I
saw by tcpdump that http wasn't tuneled:
linux@root# tcpdump -X -s 128 -v port 6661
19:47:07.980462 IP (tos 0x0, ttl 64, id 62776, offset 0, flags [DF],
proto: TCP (6), le...SSH and forwarding port
I want to use SSH from my work desk to the client site for doing some
diagnosis on electronic systems. The network will be like that:
One PC at work desk with ssh client on private LAN. SSH client is configured
for forwarding port 9000 for example (in fact, my diagnosis application). A
firewall accept the outgoing connection by port 22.
At the client site, one PC with SSH server. The connection to Internet will
be by DSL link and some servers (diagnosis servers) will be connected on
the Ethernet private network on site (by Ethernet connection on the SSH
My question is this o...ssh, port forwarding
Does anyone know why ssh connections use seemingly random port
numbers? At least it appears that way in a tcpdump output:
"192.168.1.201:61032 > 192.168.1.1.ssh", or "192.168.1.1.ssh >
192.168.1.201.56365" ...and others.
I'm trying to ssh in to .201 from the WAN. .1 is running a nat-
enabled firewall (FreeBSD 7.0, natd, ipfw) and is configured to
forward port 2222 to 192.168.1.201:22. But I cannot connect, and I've
narrowed the problem down to my firewall, which only has 22, 67, 80,
and 2222 open for incoming connections. Is there a specific range I
sho...SSH Port forwarding
I am running an application over telnet interface on port say 5566
So I generally connect telnet <hostname> 5566.
How to connect to the application via ssh (using ssh portforwarding.)
Thanks and Regards,
> Hi All,
> I am running an application over telnet interface on port say 5566
> So I generally connect telnet <hostname> 5566.
> How to connect to the application via ssh (using ssh portforwarding.)
> Thanks and Regards,
ssh -L 5566:localhost:5566 userid@remotehost
telnet localhost 5566
Thanks. It wo...Remote Port Forwarding
I've been trying the past few days now to set up remote port forwarding.
I've been seeing other people ask this question but never any solutions. My
scenerio that I am trying to accomplish is as follows:
Home Computer - Home FW - Internet - Work SSH Server <- VNC Viewer
Home Computer opens a plink ssh session to my Work ssh server and
establishes Port forwarding.
plink -l testuser -R 5900:localhost:5900 ip_of_remote_server
When I open VNC and attempt a connection to the Work SSH Server, the
connection fails. I try doing verbose mode for the ssh c...SSH and Port Forwarding
I'm running SSHWindows (sshd) on a Win2k server on port 2345. From a client
I can connect using "ssh -p 2345 Administrator@server" just fine. I also
have VNC running on this server at port 5900. I can configure port
forwarding by typing "ssh -p 2345 -L 1234:server:5900 Administrator@server"
and then connect to localhost::1234 on the client to establish a VNC
Now I assumed that the only port needing to be opened on my firewall would
be port 2345 but I'm finding that this doesn't work unless I also open port
5900. I'm guessing that'...ssh port forwarding
I want to use ssh port forwarding to make a secure channel between client
and server CVS. I had find a lot of info about how to setup port forwarding
without a remote login in a client (using -f option) but I do not want to
setup that in the client side but I want to setup it only in the server
side. In this way any client, without specify -f option, can use port
forwarding without a remote login.
Someone know how to setup that??
Johnny Choque wrote:
> Hi all,
> I want to use ssh port forwarding to make a secure channel between client
> and server CVS. I had find a lot of info about how to setup port forwarding
> without a remote login in a client (using -f option) but I do not want to
> setup that in the client side but I want to setup it only in the server
> side. In this way any client, without specify -f option, can use port
> forwarding without a remote login.
> Someone know how to setup that??
I think you are misreading the -f option, it doesn't allow you to use
ssh without having a login on the server, it puts the login in the
background. Not the same thing.
-bill davidsen (email@example.com)
"The secret to procrastination is to put things off until the
last possible moment - but no longer" -me
...ssh.com v126.96.36.199 slow performance with ftp over ssh port forwarding?
i am using a ssh port forwarded tunnel to secure a ftp connection between 2
both run the same ssh version, mentioned in subject.
what i do is:
ssh -l username remotehost -L ftp/10001:localhost:21
ftp/ should ensure that the data channel is encrypted via the tunnel as
well, not only the control channel.
anyways, i got a 3 mbit dsl line here, and am not able to get more than
210KByte/sec over the forwarded ftp connection. i treid the same setup to
other machines as well, same results. i tried changing the ciphers,
performance stays the same. i mean i would expect some overh...Port Forwarding: Device:Port = Router:Port?
- Webcam's IP addr = 10.0.0.140, and it's set up to
use port 8000
- Router's IP addr = 188.8.131.52, and it's port forwarding is set
up to forward port 8000 to 10.0.140.
- I can view the camera using 10.0.0.140:8000, no problem.
The Question: Should I be able to view the camera using
On Wed, 31 Aug 2011 08:13:01 -0400, "(PeteCresswell)" <x@y.Invalid>
> - Webcam's IP addr = 10.0.0.140, and it's set up to
> use port 8000
> - Router's IP addr = 184.108.40.206, and...SSH port forwarding with Cygwin
I'm trying to use my Windows box as a tunnel to a remote host.
On my Windows box I'm running Cygwin SSH like this:
me@WINDOWS> ssh -g -L 6789:remote.host.com:22
From my Windows box I can connect to the remote host:
me@WINDOWS> ssh -p 6789 me@localhost
logs into remote.host.com successfully.
The IP of my Windows box is 192.168.131.100. If I use my
machine's IP address instead of "localhost", it doesn't work:
me@LOCAL_WINDOWS> ssh -vvv -p 6789 firstname.lastname@example.org
OpenSSH_3.8p1, SSH protocols 1.5/2.0, OpenSSL 0.9.7d 17 Mar 2004
debug1: Reading configur...