CentOS 5 Networking :: Received Tcn Bpdu On Port?
Jun 8, 2009
i am using centos 5.2 . recently i have implementing transparent proxy but i faced issue. i received lots of messages in dmesg. i have 2 machine with same OS another machine are works fine with this same configuration
br0: received tcn bpdu on port 1(eth0)
br0: topology change detected, propagating
br0: received tcn bpdu on port 1(eth0)
br0: topology change detected, propagating
br0: received tcn bpdu on port 1(eth0)
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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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Mar 10, 2009
i want to resolve the above error. I'm using systemimager to autoinstall system images on pc's connected in lan. while doing this i got the error No DHCPOFFERS received. Also at the time of booting my pc it shows the message No dhcp and/or proxyDHCP offers recieved. But i've started the dhcpd deamon on my pc. Also the systemimager rsync deamon is running. The two pc's are also connected in lan properly.
Still while autoinstalling the image on client it fails showing the error message... No DHCPOFFERS recieved. what do i do in order to make my autoinstall work properly? How do i come to know whether the dhcp server is running or not? What will be the exact problem in autoinstalling?
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Aug 31, 2009
Can anyone here point me to a walk-through or discussion of how to use Webmin to set up port forwarding/NAT on a dual-NIC Centos 5.3 box? The layout will be simple:
Internet --- NIC1 [CentOS Box] NIC2 --- Switch to other PCs
We have a BUNCH of exposed services that are on special ports -- for example, to connect to one machine, you go in with [IP_Address]:12000, and to connect to another, [IP_Address]:12002, etc., etc. We're currently using OpenSuse 10.3 on this box, and YaST makes this criminally easy (you give it the incoming port number and the destination IP/port numbers and it just works). But OpenSuse 10.3 is nearing EOL, we're buying a new machine, and I'd like to use CentOS on the new one.
I've read the sparse Webmin documentation in their Wiki, and it leads one to believe that you simply insert a "NAT" rule. But there's obviously something they're leaving out. I *am* opening the ports in the firewall. But when I log in to [IP_Address]:port, it just times out. The port forwarding never occurs. The test in this case is SSH, and I know that SSHD is working properly because I can log into that machine just fine from another PC on the same internal subnet.
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May 30, 2011
i am not able to port 8080 on my CentOS VPS server.I have followed all the instuctions as mentioned on iptables wiki page.Also I am able to telnet my ip address and port number, But can not access from browser.
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Feb 10, 2011
Pl can anyone guide me to connect centos 5.5 using ethernet port to ADSL Broadband modem which is configured in PPPoe mode?
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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
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Feb 18, 2010
I want to do a simple port redirect, i.e. whatever comes trough whatever interface on port AAAA will get redirected to port BBBBI thought that iptables -t nat -I PREROUTING --source 0/0 --destination 0/0 -p tcp --dport AAAA -j REDIRECT --to-ports BBBBhowever it doesn't work, e.g. nc -v -w2 -z localhost AAAA gives:
nc: connect to localhost port AAAA (tcp) failed: Connection refused
while
nc -v -w2 -z localhost BBBB
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Jan 16, 2010
I would like to be able to ssh to a TCP port on my server and be directly connected to the serial port @ 115200 Null modem config. Does any body know how one can do this?
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Jun 18, 2010
I installed the Centos 5.5 and after the Xen. After I put a virtual machine named VM01.Initially it worked properly, I tried everything and it worked.When rebooted, I had problems with the network.I have two network cards eth0 and eth1, but eth1 does not have any ip and I use only eth0.The error that appears is:
vif0.0: received packet with own address the source address
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Jun 25, 2009
Would like to seek your support and idea about the having 2 IP addresses bind to my server.I am using a Dell Server coming with 2 Gigabit Ethernet ports -- eth0 and eth1.After CentOS 5.4 installation, if we assign 2 IP addresses 192.168.1.1 and 192.168.1.2(both in the same subnet - 255.255.255.0) to the 2 NIC. The default gateway is 192.168.1.254.We found the following phenomenon:1. If we unplug the cable connecting eth0, eth1 will be disconnected as well.2. The connection to the server, like SSH, FTP, experience frequently disconnection.My questions:1. If we want to connect both cables to the 2 ports, how can we make them independent and actas normal? That means both ports are functioning independently.2. Is the any build in function in CentOS that can bind 2 NIC as 1?
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Mar 24, 2010
I have a CentOS5 box I use to run ASSP for Anti-spam. It has a single NIC. I configure network settings using Webmin. I have two Internet connections managed by different routers.
Router 1 - 10.0.0.254 255.255.255.0
Router 2 - 10.0.0.250 255.255.255.0
CentOS - 10.0.0.30 255.255.255.0
Both routers port forward traffic on port 25 (SMTP) to the CentOS box. The SMTP connections only work for the router that is the default gateway on the CentOS box! If Router 1 is configured as the default gateway in CentOS then I can Telnet to that routers WAN IP on port 25 and successfully send mail! On Router 2 I get no connection unless I change the default gateway in CentOS to be the IP of Router 2 thern Router 1 SMTP connections will not work! I imagine that CentOS is sending out it's responses to the default gateway instead of the Router that initiated the port forward?
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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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Nov 28, 2010
1. I've just installed Centos 5.5 on a dell machine with 2 network interfaces, and have disabled SELinux.
The output for the command sestatus is: SELinux status: disabled
2. Am I right to think that iptables is not a concern since SELinux is disabled? In any case, the output for the command "iptables -L" is:
Chain INPUT (policy ACCEPT)
target prot opt source destination
ACCEPT udp -- anywhere anywhere udp dpt:domain
ACCEPT tcp -- anywhere anywhere tcp dpt:domain
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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]
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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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Sep 1, 2011
I have a server hosting with in a DC and I have two subnet on 1 VLAN. how can I add all the IPs from these two subnet in one go? lets say for instructional purpose they are 192.168.0.0/24 and 192.168.1.0/24
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May 20, 2010
Im having a hanging problem with a HP dl160g6. uname -a shows:
Linux mail.xxxxx 2.6.18-194.3.1.el5 #1 SMP Thu May 13 13:08:30 EDT 2010 x86_64 x86_64 x86_64 GNU/Linux
The server was working fine since November �09 until a month or 2 ago.Sometimes (almost daily now) the machine hangs and shows the front "health led" blinking red.The services do not respond,locally i can see the login screen but when attempt to logon it freezes (the same happens with ssh).2 weeks ago i open a case in HP and the support sugest that the problem is in the X server (??), since then the system starts in runlevel 3 but the problem continues. A week ago open another case, on Tuesday make a BIOS upgrade but today in the morning the server hangs again.
There�s no strange messages in log files but... after the Tuesday hungs (before the upgrade) i can see the error msg below (thanks to the change to console mode):
Uhhuh. NMI received for unknown reason 30.Dazed and confused, but trying to continue.Do you have a strange power saving mode enabled?
Uhhuh. NMI received for unknown reason 20.Dazed and confused, but trying to continue.Do you have a strange power saving mode enabled?
adding "nohpet" as kernel parameter does not work.
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Sep 30, 2010
I have one centOS 5.5 box recieving mails done by fetchmail service and it has a 5 client pc's, is there any way that the CentOS box able to deliver the mails to the 5 local network users that is using thunderbird as MUA.
the mails is stuck in /var/spool/mail as I verified in the webmin sendmail settings
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Feb 16, 2010
I have configured NFS Server on CentOS 5.2 with IBM Web Server,which is having AIX 5.3 The IBM Web Server can upload all data onto NFS Server. Now, Today i was having slow response on IBM Web Server & by measuring the NFS, i found below error while running "tcpdump" command on CentOS Server.
tcpdump -n -i eth1 | grep 2049
18:36:37.237451 IP 10.100.19.241.2049 > 10.100.19.88.1758143293: reply ok 1448 read [|nfs]
18:36:37.237476 IP 10.100.19.241.2049 > 10.100.19.88.539981409: reply ERR 1448
18:36:37.237481 IP 10.100.19.241.2049 > 10.100.19.88.796287348: reply ERR 1448
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I have changed Network Card in CentOS. All LAN is on Gigabit Network. Also I have changed the Network Cable(Patch Cord). But,still no response.
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Jul 6, 2010
I have a server in a colocation environment where I'm allotted 25Mbps. I'd like to avoid exceeding that for obvious reasons. Is there a way I can set the link speed or at least throttle the bandwidth for all services?
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Sep 14, 2009
this should be trivial for all you big sysadmin guys My box is a firewall/gateway. ETH0 is on the Internet-side, and is fully auto-configured (DHCP client) from my ISP. ETH1 is on the LAN-side, has DHCPD enabled, and I route the traffic to/from the Internet via iptables (NATting, of course). Everything works pretty good, except for the DNS-server assignment via DHCP: how can I configure dhcpd.conf to assign the SAME dns-server I receive from my provider on ETH0 to all my PC on ETH1?
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Nov 2, 2009
Can anyone tell me if there is a port of the FreeBSD PPP daemon called MPD5? I would like to run this on my CentOS installation as I understand this is better than pptpd?
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Jan 7, 2010
A lot of activity is happening on our local server and I want to know which port is getting the most used and which daemon is using the port. I think it will be some modification of netstat command.
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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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Mar 4, 2010
I am running OpenVZ.I wanted to use the VPSs IP at a particular port to load the Servers Web Pages e.g. The IP 88.88.88.88 is the VPS IP and 77.77.77.77 is the servers main ip.My files are on the main server at /usr/local/pages/
I want to load the page from the URL: https://88.88.88.88:8888
These should load the files from the main server at /usr/local/pages/ Virtuozzo a OpenVZ panel does it. So how is this going to be possible ? Will DNAT do the trick : iptables -t nat -A PREROUTING -p tcp -d 88.88.88.88 --dport 8888 -i eth0 -j DNAT --to-destination 192.168.0.1:8888
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Jun 6, 2010
I am new to iptables. The setup tool on a VPS doesn't work. So, I am learning to insert rules. I have inserted so many and some of them show as duplicates now.
1- I want to know how to remove the duplicates. Is there a file that these rules are store in so I can go in and easily edit it?
2- Is there any other utility that handles firewall in Linux that I am unaware of? or is the iptables the ultimate door guard? This is a plain install of CentOS.
3- Since I believe I opened port 5090 but I think it still might be blocked, could SELINUX be the problem? How can I get my way around setting it to permissive or disable if I don't have access to "setup" command?
4- What is the order of iptables reading? does rule #1 supersede all other rules? or does the last rule supersede all rules prior to it?
5- Do the rules below make a fairly safe system? (except for the duplicates which should be remove) I understand that a safe system is dependent also on the applications that are allowed in this category and I am not talking about those. I am talking about dropping all other inquiries and in general is this how iptables are setup? This is what I currently have:
[root@tel ~]# service iptables status
Table: filter
Chain INPUT (policy ACCEPT)
num target prot opt source destination
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May 5, 2009
My first time installing centos server and adding it to xp home network. I am new to setting up my own network in general. I have a home windows wired ethernet xp network (simple linxs router) with 2 xp boxes and one centos5 box all connected to the same router. I just set up the centos box running tomcat on port 8080. I need to do two very basic things at this point, but am not sure what I need to do:
What do I need to do so I can:
1. Connect in firefox on one of my xp boxes and call the tomcat server running on my centos box?
2. Be able to ftp to centos box from either of my xp boxes?
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Aug 1, 2009
I have 2 server behind the netgear router on my network . win2k3 and CentOS development server, I have port forarded 80 to win2k3 server which i can access over the internet and is accessable. However I can SSH CentOS machine and portforwarded 8080 and 82 for web access, I can't access via any of the port, browsers says UNABLE TO CONNECT.. there is no firewall in CentOS machine.
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Apr 27, 2011
I'm trying to open up some ports to connect via vnc to a server running Centos 5.5. I've edited /etc/sysconfig/iptables everything *looks* fine, but I still can't seem to get access to the port I've opened (I added some newlines for clarity between commands):
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Sep 25, 2009
I have opened/added the ports 1812 and 1813 (both tcp & udp) for radius server in the firewall.
when i use the command : telnet localhost 1812 , the connection says "refused", i get the following messages code...
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