Red Hat :: Disabling IPv4 Packet Forwarding: Net.ipv4.ip_forward = 0 (CentOS 5.5)?
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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Jun 11, 2011
I have an OpenVPN(10.04.2 LTS) server running in bridge (TAP) mode. Its sitting behind a router and then a cable modem. The VPN works perfectly but I have a security concern. In order to allow the VPN clients to connect to the internet, I had to enable IPv4 forwarding on the server. Is this is a security hole? Can a hacker access my servers connection from the internet (without authenticating with OpenVPN) and access my network. Can someone use Ipv4 forwarding to access my LAN network from the WAN
I used this command to enable ipv4 forwarding
echo 1 > /proc/sys/net/ipv4/ip_forward
Without IPv4 forwarding my VPN clients can only access my LAN and router, but they cannot reach my modem or the internet.
[Code]...
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Jan 3, 2010
I have searched around, and cant seem to remember where I would change bind to only support ipv4.
Quote:
network unreachable resolving 'dns1.uidaho.edu/AAAA/IN
': 2001:503:a83e::2:30#53: 1 Time(s)
network unreachable resolving 'dns1.uidaho.edu/AAAA/IN
[Code]....
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Nov 16, 2010
what is the size of an IPV4 IP address?
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Dec 17, 2015
I am setting up a server on a Intel Nuc PC. I have a problem though. I cannot get it to find a IPV4 address.
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Jun 8, 2011
Is there a way to access today the openSUSE servers via IPv4? My ISP does not support ipv6, nor my router, and I can't install software right now in openSUSE, because it wants to access te servers via IPv6.
If would be grat to have the download.opensuse.org ipv4 address.
I really need to install some packages, they are required for my school project.
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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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May 31, 2011
When doing the ifconfig command I only receive the IPV6 address. How do I specify that I need the IPV4 address???
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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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Aug 14, 2010
I can connect & share my dual-boot PC with no problems under WinXPPro using wired or wireless. (I've another thread going trying to get the wireless-n usb adapter to work.) Two questions so I can get the wired shares to work. I want to copy beaucoup files from the Win7 PC to the dual-boot PC. When booting into XP, no problems. When booting into Ubuntu 10.04, nothing. I can see the Win7 PC but can't access it. My two questions then are these. First, is there some switch to enable fire & drive sharing under Lynx as there is under WinXP / 7? (Samba??) Second, how does one set the IPv4 address? Under WinXP it's one address and under Lynx it's another.
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Sep 2, 2009
Can someone explain me ipv4 notation like:
192.168.1.0/255.255.255.0
Does it mean "any host on 192.168.1.x" network?
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Aug 17, 2015
In one of my customers, the new internet connection have no public IPV4(using GCNAT), only public IPV6.
And there are various services that require external access, like, vpn (openvpn), a java/web system, ssh, rdp(windows).
fileServer(by vpn).
All is running ok in IPV4.Maybe, the solution is a NAT 6to4. We know this is the future, no more public IPV4.
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Mar 21, 2010
setting up NAT and firewalling for both IPv4 and IPv6. The machine is headless, so everything must be configured via CLI. I've done all IPv4 firewall configuration writing iptables rules in a bash script so far
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Jan 23, 2011
I'm working in windows, and that's why I have been able to access the network. In F14, I was able to access the router address while the internet access ain't. Tried restarting network, and still the problem persists. Tried [URL] and the only thing that i've infered is that IPv4 Failed: FATAL plus, the routing table showed 0.0.0.0 as one of the entries (Gateway). So, i've deleted the wired network configuration from the Network Configuration and checked whether the os would pick it up automatically. It still didn't work.
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Jun 28, 2011
I had some fun here, with my local Cyrus IMAP daemon. I "updated" the machine to openSuse11.4 (from 11.2) by doing a fresh install. Because some of my involved HW here isn't capable of IPv6, I switched it off using yast2:
Netzwerkgeräte/Netzwerkeinstellungen [my translation: Network devices / Network Settings] Globale Optionen [global options] Removed the mark on "IPv6 aktivieren" [activate IPv6]
Then I had a hard fight with Cyrus IMAPd, mostly caused by user brain damage on my part... But one thing really looks like a problem on the Suse side of the fence: My /etc/hosts missed the "localhost"-entry for IPv4 ! This was the contents:
Code:
# special IPv6 addresses
::1 localhost ipv6-localhost ipv6-loopback
127.0.0.2 godot.site godot
[Code].....
I haven't seen this effect on 11.2 here and I haven't seen it on "my other" machine (running 64 bit version of Suse 11.4). But there I think IPv6 is still activated. I will check this, as soon as I get there.
Should this be reported as a potential bug in 11.4 ? Or is there some way, I could have messed up this. (No I didn't edit /etc/hosts by hand, before I corrected this thing)
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May 6, 2011
I've got a Ubuntu Linux box that has two IPv4 addresses and an IPv6 address. This is my current /etc/network/interfaces:
auto lo
iface lo inet loopback
auto eth0 eth0:0
[code]....
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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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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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Oct 15, 2010
Fedora 12 running under VirtualBox 3.2.8 w/ Bridged networking
Host OS Windows 7
I have 3 IP addresses set up in on my Fedora 12 installation:
Directory: /etc/sysconfig/network-scripts/
ifcfg-eth0 -> 192.168.0.170
ifcfg-eth0:0 -> 192.168.0.171
ifcfg-eth0:1 -> 192.168.0.172
Hostname is configured to host associated with 192.168.0.170 in /etc/hosts
When I reboot and execute
# ifconfig
eth0 is associated with the 172 address and the other addresses are not active. After I run
# service network restart
All of the addresses are active and associated with the correct interfaces. Content of my ifcfg files below:
/etc/sysconfig/network-scripts/ifcfg-eth0 :
Code:
# Intel Corporation 82540EM Gigabit Ethernet Controller
DEVICE=eth0
HWADDR=08:00:27:0A:9D:24
ONBOOT=yes
TYPE=Ethernet
BOOTPROTO=none
IPADDR=192.168.0.170
PREFIX=24
DNS1=192.168.0.1
NAME="System eth0"
UUID=5fb06bd0-0bb0-7ffb-45f1-d6edd65f3e03
GATEWAY=192.168.0.1
IPV6INIT=no
USERCTL=no
NM_CONTROLLED=yes
/etc/sysconfig/network-scripts/ifcfg-eth0:0 :
Code:
# Intel Corporation 82540EM Gigabit Ethernet Controller
DEVICE=eth0:0
TYPE=Ethernet
BOOTPROTO=none
IPADDR=192.168.0.171
PREFIX=24
DNS1=192.168.0.1
NAME="System eth0"
UUID=5fb06bd0-0bb0-7ffb-45f1-d6edd65f3e03
GATEWAY=192.168.0.1
IPV6INIT=no
USERCTL=no
ONPARENT=yes
NM_CONTROLLED=yes
ONBOOT=yes
/etc/sysconfig/network-scripts/ifcfg-eth0:1 :
Code:
# Intel Corporation 82540EM Gigabit Ethernet Controller
DEVICE=eth0:1
TYPE=Ethernet
BOOTPROTO=none
IPADDR=192.168.0.172
PREFIX=24
DNS1=192.168.0.1
NAME="System eth0:1"
UUID=5fb06bd0-0bb0-7ffb-45f1-d6edd65f3e03
GATEWAY=192.168.0.1
IPV6INIT=no
USERCTL=no
ONPARENT=yes
NM_CONTROLLED=yes
ONBOOT=yes
After booting:
Code:
# ifconfig
eth0 ....
Restart network:
Code:
# service network restart
. . .
# ifconfig
eth0 ....
eth0:0 ....
eth0:1 ....
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Aug 2, 2010
I am new to Linux so thought it would be a good learning exercise to try and setup an FTP server using linux.I have downloaded and installed Ubuntu 10 server edition and installed vsftpd, following instructions found on here I have configured the software and I can connect from an FTP client on my windows PC across the internal LAN.I have a couple of questions if I may:
1) a post on this forum suggests that local users can access the FTP server if the correct line is enabled in vsftpd.conf - I have done this and the fact that I can access it shows this is working I would think, however users added subsequently with the useradd command cannot access the server. Filezilla shows a could not connect to server error.
2) how do I give the server a fixed IPv4 address? It is currently using DHCP
3) I need to be able to put files into users folders for them to access offsite, but I don't want them to see each others filesfolders, can I do this?
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Dec 28, 2015
Had an issue on one of my Debian stable servers the other day. After doing apt-get upgrade I was prompted to do autotoremove.
It wanted to autotremove
Code: Select allStart-Date: 2015-12-21 16:25:05
Commandline: apt-get autoremove
Remove: sendmail-cf:amd64 (8.14.4-8), exim4-config:amd64 (4.84-8), sendmail-base:amd64 (8.14.4-8)
End-Date: 2015-12-21 16:25:07
After doing this I rebooted my server (a few days later). After rebooting I had no ipv4. I tried statically assigning IP addresses to no avail. Ran ifconfig eth0 down/up which got me nowhere. Eventually decided to ask "Okay, what changed". Started installing packages that were autoremoved. Had to install from the apt cache using dpkg. First one I tried was sendmail-base. Then did ifconfig eth0 down/up, which gave me networking back.
I have checked the dependencies for sendmail-base and I see nothing that would relate to networking, so I'm really confused on why this happened. I had backups of the server so I went a week back and noticed sendmail-base was installed at that time. So I went a day back, where sendmail-base wasn't installed, and installed it. Sure enough it brought back networking. I'm just stating this because it is more proof that sendmail-base was the missing component.
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Feb 19, 2010
How do I assign IPv4 and IPv6 static addresses permanently in OpenSUSE 11.2? Currently I am only able to assign either IPv4 or IPv6 static address not both. I cannot find even the interfaces file(/etc/sysconfig/network/interfaces).
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Feb 6, 2011
I'm using Ubuntu Linux as my operating system.In my network only the ipv4 is suported, and I need to access some website through ipv6. How can I do it, is there a way to tunnel from the ipv4 to ipv6.
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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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Oct 29, 2010
After upgrading from 9.10 to 10.04, a hundred or so of (for example)
Code:
error (network unreachable) resolving '14.42.117.203.in-addr.arpa/PTR/IN': 2001:500:13::c7d4:35#53: 1 Time(s)
messages appear in syslog each day. Each URL has from 2 - 6 attempts at various ipv6 addresses. My question is why is bind9 trying to resolve ipv6 addresses? I have done nothing to enable or disable ipv6 and thought that if not explicitly enabled I would not have to be concerned with it.
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Jan 5, 2011
how to make a Ubuntu 10.04 server VM look for an IPv4 address if it doesn't seem to by default?
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Mar 12, 2010
How do you I use duel stack i.e How do I use ipv6 packet inside ipv4 packet using fedora kernel 12 ?
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Jan 29, 2010
I just installed Fedora core 11 and am trying to get httpd to start, but it gives me a [failed] message. When I run it with -e DEBUG, I get an error message like: "failure in name resolution, unable to find IPv4 address of 'uaserver'" In the httpd.conf I have my hostName set to localhost.
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