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...Ports....Ports....Ports...
I have a linksys WRT54G wireless access point and I have't been able to get
voice communications using Windows Messenger or Buddy Talk. With a direct
PPOE connection to my isp they voice items worked fine. What ports need to
be forwarded to allow for voice?
On Fri, 08 Aug 2003 15:05:30 GMT, William Harper spoketh
>I have a linksys WRT54G wireless access point and I have't been able to get
>voice communications using Windows Messenger or Buddy Talk. With a direct
>PPOE connection to my isp they voice items worked fine. What ports need to
>be forwarded...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,...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...Why is port forwarding more secure than opening up a port?
I have never understood this very well, here is my current grasp of it..
If I open up port 110 on my router:
1. If hacker is probing random IP addresses on that port, I will be flagged
as open and he will come back and pay me a visit.
2. Any Trojans, viruses, or other malware that works its way into PCs via
port 110 will eventually stumble across my open port and infect me.
Alternatively, if I "forward" port 110 to say 192.168.0.5 (my pop3 server
1. If hacker is probing random IP addresses on that port, will I will be
flagged as closed? stealthed? worth a second visit?...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: 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 = 22.214.171.124, 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 = 126.96.36.199, and...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...ssh remote port forwarding
I have a little problem using ssh and remote port forwarding. Here is
the problem: I have one machine (A) behind a nat firewall that I'd like
to be able to access from the outside via ssh. Unfortunately I have no
control over the router, so no DMZing it.
So I was thinking of sshing from machine A behind the firewall to a
machine outside the nat (machine B) and using reverse port forwarding on
that machine. Then I could ssh to machine B and that would then forward
the connection to A.
so far I run this on A:
sudo ssh -g -N -R 2222:127.0.0.1:22 machineBusername@machineB.something
then running the following in the outside world:
ssh -p 2222 machineAusername@machineB.something
yields a time out.
I'm a bit confused on how to get this to work. Is what I want to do
pricipally possible and if so, what can I do to make it work?
s v e n (dot) d (dot) m e i e r (at) g m x (dot) n e t
In article <email@example.com> Sven <firstname.lastname@example.org> writes:
>I have a little problem using ssh and remote port forwarding. Here is
>the problem: I have one machine (A) behind a nat firewall that I'd like
>to be able to access from the outside via ssh. Unfortunately I have no
>control over the router, so no DMZing it.
>So I was thinking of sshing from machine A behind the firewall to a
>machine outside the nat (machine B) and using reverse ...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...Port security on a Catalyst 4000
I've got port security configured on a catalyst 4000, running catos
7.6.3. The config command is:-
set port security 6/18 enable age 0 maximum 1 shutdown 0 unicast-flood
enable violation shutdown
When I patch a workstation into the port, it learns the mac and shows
it as secure. When I subsequently remove the workstation, a "show port
security 6/18" shows no secure address. I can then patch a different
workstation into the same port, and it learns the new machine's mac
As I understand it, the first machine's mac address should be learnt,
and the port should be...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...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.
7.2. TCP/IP Forwarding Channels
When a connection comes to a port for which remote forwarding has
been requested, a channel is opened to forward the port to the
uint32 sender channel
uint32 initial window size
uint32 maximum packet size
string address that was connected
uint32 port that was connected
###string originator IP
uint32 originator port
The 'originator IP address' is the numeric IP address of the
from where the conn...Socket connection to port fails despite port open / listening !
I have opened port 5129 on 2 linux machines (CENTOS) and they are
listening - 1 machine accepts socket connections from a third windows
machine (all on same network) and the 1 doesnt !! What can I check ?
1- I ran this to verify ports:
RESULT: 5129 jack
2- "netstat -tap" shows its listening :
tcp 0...FTP port forwarding in SSH.. Secure??
I was trying the "FTP Port Forwarding"
to secure the FTP transfer). I really like it, but I have a question:
On the unix manual pages (man ssh2), the description of the "-L"
option indicates that part of the connection is not secure when you
use FTP Port Forwarding, could someone please explain me what part is
not secure? Is it referring to the FTP data which is non-encrypted
inside the tunnel? Below is text from manual
page for F-Secure SSH2
...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 ...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...port forwarding for multiple ports
Is there any way to do a port forwarding (ssh -L
localport:remotehost:remoteport) for a range of ports?
If do not, can I do a port forwarding dinamically? (is there any
application that do something like this?)
email@example.com (RFT) writes:
>Is there any way to do a port forwarding (ssh -L
>localport:remotehost:remoteport) for a range of ports?
Not readily that I'm aware.
>If do not, can I do a port forwarding dinamically? (is there any
>application that do something like this?)
There's the -D command (which supports SOCKS right no...port forwarding/ opening port
i'm having P4 2.4 256MB RAM with Win XP SP-2 Pro installed.
i'm using 256 kbps connection using adsl2+ router SmartAX MT882 ADSL
Router from Huawei, china
its having NAT & built in firewall.,,, i'm also using Win XP Firewall
to protect my pc..
i want to know how to use port forwarding & how to open port on router
so that i can establish connection, also i didn't understand the UDP &
TCP, what is it all about?
i want to open port for radmin connection...
also, how to know that how much secure my pc is from internet... any
i have referred to router ...port forward / port changing
I have my router set up to port forward various ports across, eg
ExtIP:25 -> Mail:25
ExtIP:80 -> Web:80
but I cant figure out how to make the ports different. Eg i have another
interal web server which i want to make available externally...
ExtIP:8000 -> OtherWeb:80
what is the exact command for this?
ip nat inside source static tcp 192.168.176.150 80 interface Dialer1 8000
but I dont seem to be getting anywhere.
It's an 827 running IOS 12.3(15).
Never mind, I have it working now. Mistyped the port in my external access
My ...how to have ssh fails if remote forwarding fails
I'm using this command just to forward a port on a distant host:
ssh remotehost -Nnx -o ControlPath=none -o BatchMode=yes -R
I'm running this command in a while loop to have it always up even if
the connection timeout because connectivity problem. And sometimes, when
it is relaunched, it fails because of the following error:
Warning: remote port forwarding failed for listen port 2222
In this case, I'd like ssh to exit and my while loop will launch it
again until it succeed. Is it possible ?
Note that with the -Nnx options, if the TCP forwarding failed, the
command is pretty useless.
Thank you for your help
On May 30, 4:56=A0am, Loic <lll...@free.fr> wrote:
> I'm using this command just to forward a port on a distant host:
> ssh remotehost -Nnx -o ControlPath=3Dnone -o BatchMode=3Dyes -R
> I'm running this command in a while loop to have it always up even if
> the connection timeout because connectivity problem. And sometimes, when
> it is relaunched, it fails because of the following error:
> Warning: remote port forwarding failed for listen port 2222
> In this case, I'd like ssh to exit and my while loop will launch it
> again until it succeed. Is it possible ?
> Note that with the -Nnx options, if the TCP forwarding failed, the
> command is pretty useless.
Won't 'autossh' serve your ne...Symantec 200R Firewall port forwarding remote desktop security
I have set up the 200R to allow a virtual server for port 3389 so that I can
connect to our remote server using terminal services to the public Internet
IP address. It all works OK but I have disabled it because of security
reasons. Two questions:-
Is there any way to tie down this access to my own PC or network?
Can I make the port appear in Stealth mode rather than Open?
Vic Russell wrote:
> I have set up the 200R to allow a virtual server for port 3389 so that I
> can connect to our remote server using terminal services to the public
...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...how do i forward ports and allow access on some port?
I am using Norton System Works 2005 full edition (with nortn firewall)
on a windows 2000 professional OS , now i want to forward port
80,99,100 to a linux box running in the same office and I also want to
allow someone access on port 101 and 102.
Can someone help me out , how to do it.
> Hi all,
> I am using Norton System Works 2005 full edition (with nortn firewall)
> on a windows 2000 professional OS , now i want to forward port
> 80,99,100 to a linux box running in the same office and I also want to