Ubuntu Servers :: Connection On Port 143 - Iptables Are Open?
Feb 2, 2010
I am configuring an internal only IMAP server for archival emails. I am absolutely baffled why my connection is being refused. UFW is disabled and IPTABLES has a rule to allow all connections on 143 and 993. When I telnet this response is given:
Code:
telnet localhost 143
Trying 127.0.0.1...
telnet: Unable to connect to remote host: Connection refused
Even nmap shows the port closed. Here is my iptables rule:
HTML Code:
-A ufw-user-input -p udp -m udp --dport 143 -j ACCEPT
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Oct 11, 2010
Strange issue here when trying to verify firewall on Server 8.04. No ftp service running at all on server, but both nmap and netcat report port 21 as being open, even though it isn't.I am 100% sure that port 21 is not actually accessible and iptables rules are fine. Trying to connect to the port fails, yet nmap and netcat seem to report a "false positive"?Have also checked on a number of other servers I'm running, and this "false positive" seems to apply to all of them.
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Aug 5, 2009
If I forward port 80 to port 3128 for squid with an iptable rule, does port 3128 have to be open on the firewall or is this all routed behind the firewall?
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Feb 28, 2011
I've recently installed 10.10 server edition, and I must say it was a pleasant suprise, it's just the way I like it. I use it as a squeezebox-server. But I've run into a problem with the firewall. I did a portscan, which told me there are more ports open then I've told UFW to open. Among which port 25 and 119, when I telnet from another PC to those ports, the connection gets accepted, although there is no answer to any commands (as expected, there's no mail server running). Iptables print-outs also don't mention anything about the respective ports or a daemon that could be responsable, and the same applies to "ps -e" or "ps aux".
Iptables seems to be working, when I remove the rules to allow samba to work, I can't reach the shares, and when I insert them again I can reach the shares. "sudo ufw deny from any" as last rule doesn't change anything either (deny incoming is default (although I never issued the command "ufw status verbose" says it is) so it shouldn't, but ports 25 and 119 shouldn't be open either).
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Sep 22, 2010
I am getting the hang of IPTables.I've setup to open certain UDP ports but they simply refuse to show when I iptables -L.
iptables file:
$IPT -A INPUT -p udp --dport 13000 -j ACCEPT
$IPT -A INPUT -p udp --dport 13001 -j ACCEPT
[code]....
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May 16, 2011
I need the port 27015 to be open. I've opened it in iptables :
Quote:
iptables -A INPUT -p tcp -i eth0 --dport 27015 -j
But when i try :
Quote:
netstat -nan
The port 27015 do not appear as "LISTEN".
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Sep 21, 2010
how do i enable or open port in the iptables
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Jan 23, 2011
Is it possible to open dyndns port at iptables?I have a remote server which is cenots 5.5 x86 and uses iptable rules. And my local pc is windows 7 x64 and have a dyndns address as mypc.dyndns.org.I want to connect local pc with mypc.dyndns.org to remote server with iptable rules as follows.Quote:
# Xmanager
-A RH-Firewall-1-INPUT -m state --state NEW -m tcp -p tcp --dport 6000:6010 -s mypc.dyndns.org -j ACCEPT
[code]...
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Jan 11, 2011
I am at a loss how to prevent Denial of Service attacks to port 25 and not block legitimate connections from 2 Barracuda 800(s) and block smart phones such as iPhones/Blackberrys/iPhones that use the server smtp.server.com for email.
Presently for port 25
RH-Firewall-1-INPUT -p tcp -m state --state NEW -m tcp --dport 25 -j ACCEPT
The 2 Barracuda 800(s) make port 25 connections all the time, plus users with smart_phones have the incoming server type:
IMAP
pop.server.com
smtp.server.com
Is there a way to keep Denial of Service attacks from happening with iptables rules without causing blocking to the Barracuda(s) that make constant port 25 connections & smart phones that poll? I was thinking if I allowed the Barracuda(s) in these lines
-s (barracuda)24.xx.xx.xx -d (emailserver)24.00.xx.xx -p tcp -m tcp --dport 25 -m state --state NEW -j ACCEPT
Where the source would be the Barracuda going to the email server. It would be allowed, then I am left with how to allow other connections like Smart_Phones that connect via Port 25. I am thinking if I put rules in place doing connection counts in a minute it would result in errors connecting to the server and people would start complaining. Plus any limiting may result in blocking real traffic. Then would I need to allow the ISP range in the above example to accept port 25, I am still left with how to drop a flood/denial of service attack.
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Jul 4, 2009
I have a fresh installation of CentOS 5 I'm using for a server, and I'm having issues with port configuration. I have iptables running, and it started with no /etc/sysconfig/iptables file. I added a few basic rules (port 53, port 10000 for webmin), saved the file, and restarted the service. I tried connecting to webmin, scanned ports, and traffic was blocked. I set iptables to allow all traffic and restarted the service, and it still showed basically every port as being blocked. It seems port 80 and port 22 work for some reason, even when I tell iptables to block all ports.
I'm not sure what's going on here. Iptables is reading the /etc/sysconfig/iptables file, and if I use lynx localhost:someport it responds as it should according to the file. However, if I try connecting by IP, it's like there's some other firewall or something running that does whatever it's configured to do.....
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Aug 1, 2011
I have 2 servers..
let say server A and server B
On server A open ssh is configured and is running on port 2298. So from my machine I can login there using ssh on port 2298
But when I login to server B and from there I try to connect to server A I cannot.
ssh: connect to host <ipaddress here> port 2298: Connection refused
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Jun 4, 2010
I noticed you can use names for ports like ssh, instead of the actual port number in iptables, but I can't find a list of what they are?
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May 13, 2010
I'm new to linux, but enjoy using it very much, especially without a GUI, console is fun! I need to set up port forwarding. We have 3 servers, 1x running Ubuntu server 8.04 (used as transparent proxy), 1x server 2003, 1x windows xp.
The linux box has the following ips:
eth0 (internal) 192.168.1.5
eth1 (external) 192.168.0.7
Windows server 2003:
192.168.1.6
Windows XP:
192.168.1.9
Router:
192.168.0.1
The router automatically forwards specific ports to 196.168.0.7 (Linux eth0). From there I want to forward port 8585 to 192.168.1.6 and 3000 to 192.168.1.9. Is there a way that I can do this using iptables?
The commands that I think I'm gonna use look like this:
iptables -A FORWARD -s 192.168.0.0/24 -p tcp --dport 8585 -d 192.168.1.6 -j ACCEPT
iptables -A FORWARD -s 192.168.0.0/24 -p tcp --dport 3000 -d 192.168.1.9 -j ACCEPT
Would this be a correct way of doing it? My biggest problem is that I can't test it without going live, and if I go live and something doesn't work, the entire building will be left without internet, people will hate me. Also, The proxy captures all data on port 80 and forwards it to 3128 so that the proxy can monitor the usage, and a few systems runs fine with it, others however can ping websites, and internet explorer says "website found, waiting for reply" but the webpages cannot be displayed.
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Oct 11, 2010
I can seem to open port 25565 for a java application (executable jar)
I'm running ubuntu server 9 thoroughly up to date code...
Yet connections to port 25565 fail when I have the firewall enabled (sudo ufw enable)
For example canyouseeme.org says "Error: I could not see your service on port (25565) Reason: Connection timed out"
And connections to port 25565 _DO WORK_ when I disable the firewall (sudo ufw disable)
canyouseeme.org says "Success: I can see your service on port (25565)"
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Jul 10, 2010
I have two computers on a LAN. (This is history not a Bazaar question, although I have one of those too) One of them (Ubuntu 9.04) Im using as a Bazaar repository over sftp. Its been working fine for about a year. Then we had a thunderstorm that knocked out our Internet service for a couple of days. When it came back up everything is working fine accept I could no longer commit to the server. A little detective work showed that ssh was not running on the server. I started it and Bazaar then couldnt find the repository files. I still suspected an ssh problem, but port scans from both computers showed port 22 open on the server and I could do a ssh login from the client ok. Then I started fiddling with ssh on the server and now I have ssh problems on top of the Bazaar problems.
On the server I deleted then regenerated the ssh keys. Ive done
sudo /etc/init.d/ssh reload
sudo /etc/init.d/ssh start
I get a normal starting message and ps ef |grep ssh
shows /usr/sbin/sshd running. But the port scan does not show 22 open and I get connection refused at the client.
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Sep 8, 2010
Is it possible to check if a particular port is open for a particular ip in the terminal?
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Apr 14, 2009
I'm starting to like making bash scripts. It's kewl making creative ones. Right now I'm trying to make a bash script that will open up port 23 for a netcat connection. Once there's a connection, I'd like for the script to open up xmms and play a sound effect, as well as echo a txt file to the desktop saying that a connection was made at this specific time. When I execute the script, it stops exection at the first line. So far I have this:
sudo nc -lvnp 23
while [ 1 ]
do
[code]...
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Apr 6, 2010
I can't open 754/tcp por for kerberos propagation, the service is krb_prop.The file /etc/xinetd.conf:
Code:
defaults
{
[code]....
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Feb 25, 2009
I tried to see if my port was open but got a message saying Error: I could not see your service on 58.164.165.88 on port (80) Reason: Connection refused could someone us out here
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Apr 18, 2011
Is there any way to verify if packets being trafficked over a certain port are valid for the service you want to use this port for?
One obvious example that probably clarifies my question:
When I open port 443 (outgoing or incoming) for https/ssl traffic, I don't want this port to be used for say openvpn traffic.
Thus: when someone wants to surf to a website with https, it should be ok but if someone wants to connect to his home openvpn server over that same port, it should be blocked.
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Apr 4, 2011
I'm trying to use iptables in order to forward all the incoming packets for port 5555 to port 5556 on the same server (192.168.2.101).
I wrote the following commands:
iptables -A PREROUTING -t nat -i any -p tcp --dport 5555 -j DNAT --to 192.168.2.101:5556
iptables -A FORWARD -p tcp -m state --state NEW -d 192.168.2.101 --dport 5556 -j ACCEPT
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Jun 20, 2009
I am running lmgrd on CentOS5, but it returns Failed to open the TCP port number in the license. The port is 27000, how can I open that port?
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Feb 20, 2010
I'm using a Debian servers, as router/firwall.. I've two ethernet interfaces into the server, one for wan and one for lan. The i use SNAT so my LAN clients can access the internet throgh the debian router. That is working... Now i want to be able to access servers on the LAN site from the WAN site, and i wanna use port address translation (PAT). I have a FTP server running on a lan server, so i'm trying to portward port 21.
iptables -t nat -A PREROUTING -p tcp -i eth1 -d (WANIP) --dport 21 -j DNAT --to 192.168.1.2:21
When people try to access my FTP from the WAN site, they are redirected to the local FTP server, and they are promted for crendentials, but when the credentials are typed, and the local ftp server should answer the wan request, the connections dies.
The wan clients are being promted for credentials, so they are redirected to the local lan server, but after that the connections dies, so i think there is some kind of nat problem, when the local lan server is trying to respond to the wan request..
Here i my iptables script:
#flush table
iptables -F
#input regler
[code]....
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Mar 25, 2010
I have a mail server on which I would like to block port 25 on my eth0 for everyone except our external spam filter. the problem is that I want our users to be able to connect via port 10025 which is forwarded to port 25, which then is blocked...
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Apr 16, 2011
I am running Ubuntu server 10.10 and trying to setup iptables rules in /etc/if-up.d/iptables
Quote:
root@host# cat /etc/network/if-up.d/iptables
#!/bin/sh -e
iptables -A INPUT -m state --state ESTABLISHED,RELATED -j ACCEPT
Problem is that iptables doesn't get updated and I don't see them when iptables -L is executed after reboot.
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Nov 26, 2010
I am unable to restore my iptables from iptables-save after upgrading Fedora. I cannot get iptables-restore to work, and I have resorted to entering rules manually using the GUI.
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Jan 7, 2011
I am merely trying to change the port for my ssh server.However it isn't changing.I edited my ssh_config file to:
Code:
# This is the ssh client system-wide configuration file. See
# ssh_config(5) for more information. This file provides defaults for[code]...
When i try to connect to my server via port 443 i get a connection refused error. However when i try to connect via port 22 it connects. Since that didn't work, i tried restarting the entire server.To restate, i changed the config file and restarted ssh then the computer, however the port didn't change.Ohh and yes my router is set to port forwarding on port 443, though it doesn't matter since I'm inside the network.
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Mar 3, 2009
In a little over my head here but eager to learn. Running Fedora 10 on an IBM T41. Trying to set up a local server so that I can run PHP and test webpages locally (I'm a client-side web designer). Went through the SendDerek tutorial and everything went great until I tried to check the port with canyouseeme.org. I get "Connection timed out" every time.
- The httpd service is started via the terminal.
- Port 80 is unblocked via "Firewall Configuration."
- I set up port forwarding on my router.
What am I missing? I just want to be able to have the local computer run my PHP scripts instead of having to upload them to a remote server every time I make a change.
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Jul 15, 2011
i want if a port (exp. 1001) have 20 connections that the next new connection forword to an other port (exp. 1002).
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Apr 6, 2010
i am running ncat (netcat's new version from nmap) on centos . I am listening on different ports. My question is , is it possible that when a connection is received on a port say 123, i redirect this connection to a different port and use the 123 port again for listening connections. ncat has an option -k which u can add with -l , it will force fully listen on the port. It can accept multiple connections on a single port but i want that once a client connects on to 123 port, he is forwarded to some other port and no longer on 123.
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