Ubuntu Networking :: Open Ports - How To Explicitly Check IPV4
May 4, 2010
Normally I use 'netstat -an' to determine if a daemon is listening on a specific port. The excerpt of this command below doesn't list things like vnc (5900) on ipv4. It does however show it on ipv6. My issue is I want to know how to determine if it is indeed listening on ipv4 as would normally be seen with 0.0.0.0:5900. It would appear that all ipv4 ports are internally being redirected to ipv6. Of course this does simplify things, but it also leaves me unable to reliably determine the ipv4 listening status. How I can tell at a glance if a specific ipv4 port is being listened on? Is there a way to force netstat to list the ipv4 listens specifically?
Code:
art@eee1:/proc/sys/net/ipv6$ netstat -an
Active Internet connections (servers and established) .....
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Jul 3, 2011
I'm running a native dual-stack (ipv4 & ipv6) dsl connection.So, I've been adding firewall rules, cleaning up unwanted processes, etc to tighten security.I'm left with only 3 processes that are listening to ports. mysql, ipp & ssh.Still not quite sure I need mysql. I run Amarok but without using a database, so I don't actually use sql for anything that I'm aware of.Anyway, my question is;Is it possible to make any any of these processes listen to ipv4 only or ipv6 only? Is there a distinction there at all?
Example- ssh is currently listening to port 22 on both tcp & tcp6. I do all my ssh connections using 'ssh -6', so, Can I make ssh listen to tcp6 only, or ignore tcp ?
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Apr 6, 2010
A few months ago I installed Ubuntu 9.10 on my girlfriends laptop, on her request, as she didn't like Windows any more. Since then the internet connection periodically slows down due to too many open ports/connections. Always when this happens I call our ISP and usually there are around 80-200(!) active connections to various IP's.
She is not downloading torrents or anything.
She only uses Firefox and a few open tabs as people do.
Skype is open.
Wireless internet connection.
I am thinking either Ubuntu is updating more or less constantly or the ports/connections aren't closed "after use".
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Apr 5, 2011
I'm trying to open my ports all the way, but for some reason, I am unable to do so. I've forwarded the ports I want open in my router (I switched between two routers to make sure), I made exceptions in Firestarter, and I even added UFW rules, but when I use pretty much any and every port checking tool out there, the ports eithere back stealthed or closed.I'm not a complete noob, and I'm not an expert, but I'm p sure I'm doing everything right, seeing as there isn't much to screw up.The reason I'm trying to fully open these ports is because I'm getting this dumb 'No Incoming Connections
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Feb 4, 2010
Does Ubuntu come with a firewall preinstalled and running? I need to open port 9997 - how would I got about doing this?
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Jan 2, 2011
I have been running Ubuntu 10.10 and have found that at any time I am connected to the Internet that I will randomly see high port numbers open when doing a port scan on my computer all are in the unknown listings with five digit numbers so I don't know what is going on or who is using them. Please check your system to see if you are having the same thing happen by using network tools and filling in your local ip address in the port scan tab. If you shut down your Ethernet interface and run port scans the high ports are no longer open. this will at least keep whoever is using your ports at bay when you are not using the net.
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May 14, 2009
Since there was no response on my other post which i spent about a hour writing, ill go for something simpler. I run this on my server
Code:
# set default policy for the NAT table
iptables -t nat -P PREROUTING ACCEPT
[code]...
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Jan 30, 2010
I would like to open some port from IN to OUT pop3,smtp.whenever i tried to add some rules to existing iptables it gives me an error.Applying iptables firewall rules: iptables-restore: line 21 failed
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Apr 12, 2010
I forwarded ports 28900(TCP/UDP) and 5029(UDP) to my linux box for a game. Testing my ports with a website now shows these ports as "connection refused" rather than "timeout" which means the connections are getting to my system but the iptables are blocking them. But I added 28900 as a test and it still won't accept anything on this port. This is my output of iptables -L
root@BPC3:~# iptables -L
Chain INPUT (policy ACCEPT)
target prot opt source destination
ACCEPT tcp -- anywhere anywhere tcp dpt:28900
Chain FORWARD (policy ACCEPT)
target prot opt source destination
Chain OUTPUT (policy ACCEPT)
target prot opt source destination
ACCEPT tcp -- anywhere anywhere tcp dpt:28900
What do I need to do exactly to add exceptions for 28900 TCP/UDP and 5029 UDP?
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Apr 16, 2010
I need to ensure ports 6112 through 6119 are open. I tried using Firestarter to do this, but when I search for what ports are open, it says none of them are. I use Ubuntu 9.04.
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Aug 19, 2010
I'm trying to set up an SSH connection from my school to my home, but not on port 22. I originally tried port 2222, but it didn't work. I called my school IT people and they said they block that port. I asked if they care if I set up an SSH and they said no, but that they wouldn't tell me which ports are blocked and which are open for "security" reasons (which I guess I can actually understand). They suggested just using port 22 or 222, but said if a ports open I can use it.
My question is, can I check ports without setting up SSH? It seems like a hassle to try a different port every day on my home SSHD file, come to school, see if it works and repeat. Is there a way I can check my computer home for connections that could connect, even if there isn't a service listening? I don't know how to do that, or even if its possible. If not, I suspect I'll just try a few until I find something that works, or just go ahead and use 22.
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Jun 28, 2011
Yesterday I switched from CentOS to Ubuntu, and wanted to install TeamSpeak3 which runs on ports 9987 UDP and 10011 TCP. The TeamSpeak3 worked fine on CentOS before this.
It appears to be running and netstat -an reports:
Code:
udp 0 0 0.0.0.0:9987 0.0.0.0:*
tcp 0 0 0.0.0.0:10011 0.0.0.0:* LISTEN
I believe the only firewall for Ubuntu is "UFW", am I correct? If so, "ufw status" reports:
Code:
Status: inactive
I do have other things running on UDP (Counter Strike Source servers) and people can connect just fine.
When I telnet localhost 10011 I get a response from the TeamSpeak3 server:
Code:
Trying 127.0.0.1...
Connected to localhost.
Escape character is '^]'.
TS3
Welcome to the TeamSpeak 3 ServerQuery interface, type "help" for a list of commands and "help <command>" for information on a specific command. However, telnetting from outside just gets no answer, this is what leads me to believe it is a firewall in the way.
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May 7, 2010
I've installed a fresh copy of the latest 10.04 distro, lucid lynx and have problems connecting to the machine via ssh because the ports are all blocked (using nmap to check). In past releases, changing the gdm.conf flag "TCPDISALLOW" from true to false would fix this. In the new /etc/gdm/gdm.schemas, I've tried making a similar change, but it's still not opening things up. I've downloaded gufw and have made sure the firewall is off. So, I'm not sure what to try next.
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Oct 29, 2010
I'm forging a gateway server, We have 2 Internet connection that goes to a load balancer router, and goes to my centos server and from our server goes to a switch for Internet distribution or routing.
OS-CentOS 5.5
[root@server etc]# uname -srio
Linux 2.6.18-194.el5 i386 GNU/Linux
My eth0 and eth1 has the following configuration and IP
[root@server etc]# cat /etc/sysconfig/network-scripts/ifcfg-eth0
# VIA Technologies, Inc. VT6105/VT6106S [Rhine-III]
DEVICE=eth0
BOOTPROTO=none
[code]....
Disabling IPv4 packet forwarding but i already changed it to 1 at sysctl.conf One of the online forum says i need to configure the named.conf deleted some and run it(named.conf) and successful but still when I run network service I still get the :"Disabling IPv4 packet forwarding: net.ipv4.ip_forward = 0" The network is getting the IP range but it doesnt get any Internet connection.
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Apr 20, 2010
How do I open ports 5198/udp and 5199/udp on a slackware based firewall?
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May 27, 2011
How do i test a Debian server using Lynx to test if there are open port externally?With GUI i use Shields Up from grc.com.In text mode with lynx - i don't know how to test the ports
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Jul 26, 2011
I set up a vnc connection to my machine the other day and while doing that checked out any open ports.To my astonishment my ftp port is open, although I double checked the firewall and there's no check in the checkbox for the ftp port. I didn't add a "other ports" rule or anything as well.So, how would I be able to fix that?
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Apr 19, 2010
Current problem: fresh, clean install of Ubuntu 7.10 on known good hardware does not use/produce/get/have an IPv4 associated with eth0, so cannot connect to my home network for Internet access.
Background: Have been wanting to build and maintain a home file server for some time now. Have also been wanting some hands-on practice to help me progress from Noob to Intermediate, eventually advanced Linux Tech. (I have two decades of tech support experience, but only small fraction of that using command lines and almost zero Linux.)
Anyway, every time I download and attempt to burn a recent distro on my Vista Shuttle, I only end up making drink coasters and mini-frisbees. so I thought that I might have better luck if I used a Linux Workstation to download and burn a server distro.
That's where I an now. I took one of my fully functional WinXP systems offline, replaced the WXP HDD with an old 3.2 GB, dug out my 2008 edition Linux Bible, popped in the DVD that came with it, and installed Ubuntu 7.10.
Everything else seems to have progressed smoothly, but I cannot seem to get the onboard Via chipset ethernet controller to talk to the router. When I run "ifconfig" in Terminal, I see IPv6 info, but nothing for IPv4.
When I try to configure eth0, it doesn't matter whether I set it up for DHCP or static... nothing works.
Is there a command line tht I can use in Terminal to manually configure eth0 to use IPv4?
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Aug 2, 2010
Our router is pretty old and only capable of giving fixed ip and there is no support for IPv6. Via the gnome networkmanager I try to set a manual IP to 192.168.1.123 and a netmask to 255.255.255.0 and a default gw at 192.168.1.1 . However, this does not work.
If I open a terminal and type:
Code:
sudo ifconfig eth0 inet 192.168.1.123
sudo route add default gw 192.168.1.1
Then I get a perfectly valid connection to the internet.
ifconfig by it self returns:
[Code]....
ffor me it seems that the gnome network manager doesn't save the information that I gently ask it to.
I can fix it with the CLI commands, but I would like to know whats going on.
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Jul 27, 2010
I'm locking down my laptop. I know I can use a firewall to ensure nothing gets through that I didn't catch, and I certainly plan on using one, but in the meantime, I want to know what exactly is running on my system.
nmap localhost returns:
Code:
james@james-linux:~$ nmap localhost
Starting Nmap 5.00 ( http://nmap.org ) at 2010-07-26 23:33 CDT
Warning: Hostname localhost resolves to 2 IPs. Using 127.0.0.1.
Interesting ports on localhost (127.0.0.1):
Not shown: 994 closed ports
PORT STATE SERVICE
25/tcp open smtp
111/tcp open rpcbind
139/tcp open netbios-ssn
445/tcp open microsoft-ds
631/tcp open ipp
2049/tcp open nfs
Nmap done: 1 IP address (1 host up) scanned in 0.18 seconds
However, I know that localhost goes back to the loopback interface, 127.0.0.1. So, to see what was really open, I ran nmap 192.168.0.108, which is my laptop's IP at the moment.
Code:
james@james-linux:~$ nmap 192.168.0.108
Starting Nmap 5.00 ( http://nmap.org ) at 2010-07-26 23:33 CDT
Interesting ports on 192.168.0.108:
Not shown: 996 closed ports
PORT STATE SERVICE
111/tcp open rpcbind
139/tcp open netbios-ssn
445/tcp open microsoft-ds
2049/tcp open nfs
Nmap done: 1 IP address (1 host up) scanned in 0.14 seconds
Now if I understand correctly, I can attribute 139 and 445 to my Samba share. That I'm okay with. What I don't know is 111 and 2049. Does anyone know what these ports are, what's running on them, and how I could turn them off, supposing that they are a security risk?
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Mar 18, 2011
I'm getting heat from the head networking office that ports 21, 110, and 143 are open. I can telnet to those ports from a remote machine (not localhost) and get a prompt. There does not seem to be anything listening on those ports according to netstat. I've tried using iptables to discard all traffic to a from those ports but I can still telnet to them. This is a lucid desktop machine.
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Apr 5, 2010
I'm using ubuntu-linux ( ubuntu 9.10)I use utility autoscan network to scan the systems available in local area network of my hostel.It shows my open TCP ports : like Ssh , Smtp , Http , NetBios-ssn , Microsoft-ds , ipp , Mysql , Postgres.Are all these services need to run all the time or I can manage the ports.Don't know much about it just want to know these ports are by default open or I can manage them.
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Sep 1, 2011
On my 10.04 LTS Ubuntu Server installation, apache2 doesn't bind to ipv4. It does bind to ipv6. I didn't notice this at first, because from my home connection I could visit the webpages without trouble. I noticed it running netstats -ta:
Code:
tcp 0 0 localhost:10024 *:* LISTEN
tcp 0 0 localhost:10025 *:* LISTEN
tcp 0 0 localhost:mysql *:* LISTEN
tcp 0 0 localhost:spamd *:* LISTEN
[Code].....
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Apr 10, 2010
I installed Ubuntu 9.10 recently. I heard that there will be no open ports in the system unless I specifically open one. How do I scan to find a open port in my system.
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Jul 6, 2010
when i enable my ufw it completely shuts me out and closed my internet connection. i installed firewall configuraiton interface and through it defined rules to accept incoming internet connections on port 80, i can see the rules are there but when i enable my firewall it just shuts me out completely again.
when i do(with my firewall enabled):
Code:
$ sudo ufw status
it gives me:
Quote:
Status: active
[Code].....
I also messed around with fwbuilder and iptables but since then deleted fwbuilder(besides i just compiled firewall policy and never actually installed it because of errors while trying to install it. Iptables I cleared with:
Code:
$ sudo iptables -F
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Dec 15, 2010
"Ubuntu Server has no open ports by default" - [URL]. Does this mean right after a 10.04 Server Edition installation, if a user wants to start a web service e.g. a Java process to listen on say port 8080, he would have to configure the firewall first?
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Feb 2, 2010
Just did a check on "shields up" and it says that ten of my ports are open. I get the same result with or without both shorewall and firestarter. I suspect it may have something to do with the mysql server packages added automatically during installation. Am I right. If so, what can be done about it? If not, has anyone any idea how to keep my ports closed?
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Feb 7, 2010
I'm trying to setup oracle10g but, whenever I try to go to my database homepage http://127.0.0.1:8080/apex I get an "unable to connect to" error. Only reason I can think of as to why I can't connect to it is because my ports aren't open. I also recall SELinux complaining about something awhile ago, I can't seem to bring that up any more for some reason.
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Sep 22, 2009
Linux has duplicate address detection mechanism for IPv6 and nothing for IPv4 in kernel. At boot time, initscripts take care to check for the duplicate address but when an IP address is assigned using ifconfig or ip utility, no error is generated.
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Apr 20, 2010
I have tried clean installs of Knoppix v0.6, Xandros 2.0, and Ubuntu 7.1... same issue with all. I cannot seem to get eth0 (via chip on mobo) to get/have/use IPv4. ifconfig shows only IPv6. (I cannot paste any info because linux desktop is on different box.)
End result is that I cannot get the linux desktop to connect to my lan, either with dhcp or with static ip.
I have a belkin router configured as my gateway 192.168.3.1 and nothing fancy with the setup. I have dhcp open for 192.168.3.245 thru ...254 and at most there are only 4 systems in home connecting with dhcp at any time. all other systems have static addresses.
I have two decades of desktop and lan support under my belt, but relatively small amount of command line experience and almost no history with linux (unless you count a dozen unsuccessful attempts to burn linux distro install discs on this Vista desktop).
Therein lies the start of my prob. I need to build and manage a fileserver for my home, but cannot seem to get a working installer cd or dvd to burn from anything I download.
So I said to myself, "Self," I said, "you're a tech. Build a workstaion, use the DVD that came with your Linux Bible (2008 Ed.) to install one of the linux distros on it, then download a recent, stable server distro and burn it using the linux workstation."
Unfortunately, if I cant get an ipv4 connection to my home network, I cant get out to the Internet to download any newer ISO files.
So what am I missing or doing wrong? How do I tell linux to stop trying to use IPv6 and let me use IPv4?
BTW, eth0 works just fine if I install Windows on that PC, so I know its not bad HW. Could it be a driver issue? Or do I need to use some Terminal command to turn off IPv6 and reconfigure eth0 for IPv4?
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