CentOS 5 Networking :: Port Open - Should Be Blocked
Jul 10, 2011
Recently I discovered that we were accidentally running a POP server (port 110), when we only should have been running the encrypted version thereof (port 995). This wouldn't have been a problem if the port was blocked in the first place.Isn't the default iptables setup on CentOS to block unspecified ports? Specifically, this line from /etc/sysconfig/iptables
-A RH-Firewall-1-INPUT -j REJECT --reject-with icmp-host-prohibited
Right? Well, this doesn't seem to be working for me. I added some rules to allow additional ports and commented out a couple (crucially port 110), but for some reason, port 110 is open.Here is /etc/sysconfig/iptables and the output of iptables -L below that:
# cat /etc/sysconfig/iptables
# Firewall configuration written by system-config-securitylevel
# Manual customization of this file is not recommended.
*filter
:INPUT ACCEPT [0:0]
[code]....
Why isn't "-A RH-Firewall-1-INPUT -j REJECT --reject-with icmp-host-prohibited" doing what I think it should be doing?
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May 17, 2010
Last night I installed all the updates that were available for CentOS. Today, I discovered that all connections to port 25 (Sendmail) are being blocked except connections coming from localhost.
I tried disabling the firewall to see if anything would change but it is still blocked.
If it is not the firewall doing the blocking, what else might it be?
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Jan 28, 2011
I have Linux server (centos) in my company , Network is shared through this linux squid proxy server to Windows client .
How to open port 995 and 587 for Windows client because Outlook are not working in Windows Client ...
How to open this port for Windows Client.
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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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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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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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Apr 27, 2010
So I set up an Ubuntu 10.04 server with apache2 installed, but for some reason I can't get to it from my browser. the iptables have all changed directories in 10.04 so I can't find the iptables. Apparmor wasn't the problem. The network hard ware is not the problem.There is something inside of 10.04 that is blocking port 80. I can ping it all day using the ip address but when I ping it useing http://ipaddress it can't find the host
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Dec 26, 2009
we are going to install ASTERISK remotely, hence the port 22 in the server has to be open ,Can somebody reply me with exact commands?I tried these commands and got these results
Command : cat /etc/services | grep xxx
Result : No Such file or directory
Command :netstat -nan | grep 22
[code]....
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Sep 18, 2010
I can't seem to establish a conncction to my site (that I'm hosting in the same computer as the gFTP client- running Lucid Lynx desktop as a server). My site is 'out there', with a domain etc. and also I work on it with localhost. I wanted to use ftp as Joomla has a 'ftp layer' for files permissions etc. But it keeps saying that I can't connect, or the connection 'was reset by a peer' whatever that means. For 'hostname' I use site.com (site is my site's name) and even tried the whole thing like http://www.site.com (I clicke on 'connect to remote, and enter that in the url). or just put it where 'host' goes (when I'm not using localhost) For user name and pass, I just enter what I usually put to access the administrator's back panel in joomla, but maybe I am supposed to use what I use to log on to ubuntu when I start my computer? note sure. Anyway I used a telnet command in the terminal and found that port 21 was blocked. MY isp says they don't block any ports so I don't know. I was able to do this last year so I don't know what is so hard about this lol In the router, I have 'ftp 21 to 21 and ip address 192.168.1.100 (ip is the same for http which is working as I have my site up) now it seems to be open as I used a command at the terminal (found from google). It's open but my ftp still can't connect to my server either localhost or to my site. there is no firewall blocking it and I think my router is set right.
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Jan 26, 2010
Here is my network diagram ADSL router----firewall--LAN inside the LAN my squid is running. currently all users are working with out proxy server. I installed the proxy server inside the LAN. now all users can access web browsing ,but no other ports are working , like POP3, smtp, then some other TCP port based applications are not working. My firewall ( juniper) is created and tested the rules to allow the POP3 and smtp and selected poprts which is working , but I redirected through squid proxy server the clients are not able to access. where do I have to create rules?
** in squid proxy( i already did in safe port list stillnot working)
** IP tables?
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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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Aug 12, 2011
I have a vps server running certain services which can be accessed via a web browser (e.g webmin control panel), but I have recently been unable to access these services from my home machine using Firefox 5.0, running ubuntu 11.04.
Example:
I can access the server on port 80 fine, eg: [URL]
However I cannot access my webmin control panel on: [URL]
The pages takes ages to load and then times out. Same with transmission-daemon on: [URL]
Everything is set up fine on my server, the ports are open in firewall etc. and I can access these pages fine from my work computer.
This has only started happening in the last day or two and had been working fine up till then. I have not messed around at all with the firewall on my home machine. I have tried other browsers besides Firefox with same result.
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Oct 21, 2010
VERY new to linux, erm but I have an issue that needs solving!I recently moved to university, where their network blocks sftp port 22, this means that I cannot connect to my FTP server which is running a version of linux.Now I've got this ftp server connected to a seedbox and it was created using the following walk through..Code:I have written this guide for a friend, but I though it would be useful for others as well.
There are several guides floating around, but I found that most always cock up in some way. This one is tried and tested to work on Debian Etch (on an OVH rps, but should apply to most servers).If there is a new stable release of rtorrent/libtorrent then I will update this guide to show you how to update it (without reinstalling the whole server).
At the bottom there are also instructions to install ftp access & some network monitoring software.Basically, I would really like someone to be able to construct the commands on how to change the listen port for sftp connection on linux or add another port to the list that Linux would use so that I could put in through putty.
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Sep 26, 2010
Ok For some reason I open my ports in security and firewall. I open ssh and other ports and port 7001 for example but when I go to check to see if they are open or try to connect to them. It shows that they are still closed. I am using - [URL] Also yes my ports are open on my router. I know my router works fine with opening ports because I have shoutcast setup on another computer with xp that is currently running. I am willing to pay for who can ever get this fixed for me...
I open the ports in graphical mode.
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Mar 2, 2011
All ports are blocked only 22 and 80 are open. I scan localhost and ports are open. When I scan IP address ports are blocked.I have no firewall rules.
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Sep 2, 2009
On our server port 25 is open for sending email. I want to open port 587 too in our firewall.If I have open tow ports 25 and 587 for out going email it is not going to make any problem? my server is Centos 5 I am using webmin to access to our server.
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Mar 28, 2011
So I have two ssh servers I connect to regularly that do not use the standard port 22, so I use the "-p" flag to connect to them. This works flawlessly EVERYWHERE except on my girlfriend's work network. When I am on that network (same laptop), I can ssh into servers which use port 22, but not the other servers on this alternate port.Is there any way OTHER than ssh'ing into a machine I can access and then ssh'ing again from there to my destination (which, by the way, does work)? I want to make a direct connection for speed and security reasons.
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Jan 20, 2010
I get today a server with CentOS.. and someone told me to block access to port 22 for all IP's except my.. so I did
Code:
iptables -A INPUT -p tcp -s my_ip --dport 22 -j ACCEPT
and after
[code]...
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Apr 16, 2011
The server I'm running is virtually stock CentOS - it's running on a xen virtual host, started as CentOS 5.1 (32 bit) when that was fresh, it's at 5.5 now and updated nightly. All packages except postgresql and php are from CentOS and EPEL.
I'm running dovecot on it, and for long time, squirrelmail connecting via localhost was good enough. All external ports were firewalled by the CentOS firewall (just 25,80,443,custom ssh are currently open).
Now I need to allow an external imap client to connect.
I have generated ssl key and configured the dovecot configuration and it should be good to go, but gosh dangit, I can't remember how to open the port in the configuration.
I did it before when I set up ssh to run on a non standard port after I got sick of constant brute force attack on port 22, but I can't recall what I did and the various tutorials I find online all tell how to do it with the GUI tool, but I don't have any GUI stuff installed.
system-config-securitylevel-tui
Is I'm pretty sure what I used to open up my custom > 1024 ssh port, but I can't remember how I used it to open that port and it doesn't seem intuitive. Also, do I need to use 993? I'd almost rather use something custom above 1024, as long as thunderbird supports it (don't care about any other mail client)
Finally, my smtp server is postfix and port 25 is already open (but not an open relay, I check it about every 3 months). For requests to send mail from a client, I would really like some authentication of some type - as in only relays for IP addresses that have recently successfully logged in the secure imap port.
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Jan 22, 2010
I found that I can not use the UDP port on FC 12.I new install one FC 12 , but when I use the next command nmap -sU localhost.I found all udp port has been filtered.I don't know how to open the udp ports . for I need use some udp port.I use iptables , but not working. Why ?
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May 23, 2010
I just installed apache. I didn't change the configuration files at all except add Quote: # added servername to avoid the could not determine fqdn error ServerName myname.homelinux.org to apache2.conf. Apache is working locally (I get the `it's working' screen at [URL]). However, I cannot access my computer from an external computer by going to [URL], which is equivalent to [URL] -- [IP address changed slightly for privacy] Here is a screenshot to my router settings. I disabled the filter for port 80 on the router. here shouldn't be a firewall, unless it's automatically installed with ubuntu 10.4. (sudo ufw status says `inactive'.)
I checked my ports from [URL] and indeed port 22 is open (ssh-ing into my computer externally is not a problem), whereas port 80 is closed. What step in opening up port 80 am I missing? (I also made sure my ISP isn't blocking port 80.)
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Jun 17, 2010
I would like to test myself if port 5060 is open for UDP packets.
I got a few shell accounts outside of my ISP that run Linux or different BSDs. Does someone know a common program where I could send UDP packets to port 5060 of the IP address that Virginmedia assigns to me and then I would need a program on a PC within my network who reads them _if_ they get through.
Background of all this is that my VOIP phones from two different VOIP providers are offline since last Monday.
One service provider confirmed that another VOIP client is online with the same service provider Virginmedia but in a different area.
So, while I don't know how long does it take that someone from Virginmedia can tell me if their port 5060 is open for UDP, I would like to find out myself in the meantime.
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Sep 3, 2009
I have a problem sending of file attachment using Instant Messengeri have a firewall using firestarter, if i used outside firewall they can able to recieve my file in instant meesenger but if i used firestarter it always cancelled my sending of file attachment....
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Mar 30, 2010
I am running RHEL 5.3 and attempted to open port 4470 for an application that will use the port. I used the graphical interface to open the port, just as I have for other ports such as 4750.I can telnet to the server with:telnet server 4750
If I try the other port that I'm trying to open:telnet server 4470
I get "Could not open connection to the host, on port 4470: Connect failed."I have restarted the network and iptables services.I have turned off the local firewall and it still did not work.
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Mar 13, 2010
needing to open a port in ubuntu, then use it for my VirtualBox Pc.My VirtualBox is running - Windows XP I have a router connected to my network - Linksys WRT54G Now lets begin, I have tried opening via there router homepage. But when I go to [URL] and test port 4900 is still says that it is closed.
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Aug 18, 2010
No matter what I do, i cannot get port 3100 to open. This is for a new MMO i am CBT on. I know it works on windows because that is how I installed it and played. But I prefer being on Linux. Majority of all other MMOs work fine. Just this one has to have udp 3100 open.
The following is a rough output of all the methods I have tried with no success. As you can see I have done some extensive research first before posting here.
Now its become a lil bit of an obsession.
I cannot get the following command to work:
And yes I tried the "spaces" in different places thinking that was the prob. So i cannot see if 3100 is in the list or not
I eventually turned on the firewall "ufw enable" add the port there, and output:
Some references
[url]
Firewall stuff: [url]
I even manually went into the router and turned it on there.
I add these lines for startup purposes.
Do I need to do something in "wine" ?
I feel i am starting to repease myself
results of "iptables -L"
Code:
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Dec 16, 2010
I have an n900 phone and I'm trying to ssh to my desktop but I'm getting an error:
ssh: connect to host 58.xx.xx.xx port 22: Connection refused
I recently started using a router for I wanted to connect to net even with n900. I've tried to open the port from the setup page of the router however it doesn't seem to work. (find below the screenshot of setup page).
I've tried to ssh through slackware I've got as a virtual machine and I have the same problem although I was able to ssh through slackware before I started using the router.
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Sep 21, 2010
how do i enable or open port in the iptables
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Feb 17, 2010
I think port 24800 is firewalled in my linux machine. i tried synergy to sue as a server in linux and doesnt work. i tried from the windows computer and works!
So... I telnet (from linux) to an address: telnet 192.168.0.1 24800 and the time is out (so a firewall is blocking this port).
My simple question: How do I open this port so i can get the synergy server in my linux box?
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May 16, 2011
I have a iptable as firewall, I want to open incoming of port 8080 so I use "# Allow forwarding of incoming Port 8080 traffic" but it didn't work? how can I open just incoming of port 8080?
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