CentOS 5 :: Under High UDP Traffic Condition - Cannot Receive UDP Packet

Jan 25, 2011

Under high UDP traffic condition, we find we cannot receive UDP packet (can be captured by tcpdump) from socket neither use bare "recvfrom" nor "select recvfrom " pair. Is there any similar problem reported from user?

Any tunning or socket establish option can help?

Or is there any improvement available from the latest version?

our using linux version is CentOS 5.5

ethernet driver version is Intel (R) Gigbait Ethernet Network Driver version - 1.3.16-k2

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CentOS 5 Server :: Authenticate/Decrypt Packet Error: Packet HMAC Authentication Failed

Sep 17, 2009

I got a problem with my CentOS server. Somebody told me OpenVPN Requires different changes inside my firewall settings. That could be the problem why openvpn wont load..I receive this error on my CentOS panel when im trying to connect into the centos openvpn (with my winxp pc):

Thu Sep 17 20:31:36 2009 TLS Error: incoming packet authentication failed from 84.xx.62.122:2622
Thu Sep 17 20:31:38 2009 Authenticate/Decrypt packet error: packet HMAC authentication failed
Thu Sep 17 20:31:38 2009 TLS Error: incoming packet authentication failed from 84.xx.62.122:2622

[code]....

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Programming :: Perl - UDP Server Receive / Send Packet To Host

Apr 1, 2010

I have found many examples out on the www for creating udp servers with sockets. The problem I am running into is after I receive the packet from a host I need to be able to send a custom made packet(I'm using RawIP / NetPacket to make my packet) back to this host. The only way to do this is seemingly through the send() function. This function however doesn't appear to allow me to specify which host to send my packet to.

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Networking :: Unable To Route Traffic Based On Packet Content

May 7, 2011

My linux machine is connected to the outside internet, and I have a minecraft server running on an internal machine (192.168.1.201). Right now, I am forwarding port 80 on the linux machine to 192.168.1.30, which is working.

iptables -t nat -I PREROUTING -i eth0 -d 192.168.1.30 -j DNAT --to-destination 192.168.1.201
iptables -t nat -A POSTROUTING -o eth0 -j MASQUERADE
iptables -A PREROUTING -t nat -i eth0 -p tcp --dport 80 -m state --state NEW,ESTABLISHED,RELATED -j DNAT --to 192.168.1.201

______________________________

I want to filter out the GET/POST requests and forward them to port 8080. I can't seem to get that working.

I've tried this:

iptables -A INPUT -d 192.168.1.30 -p tcp --dport 80 -m string --algo bm --string 'GET' -j REDIRECT --to-ports 8080

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Server :: Too Much Packet Loss While Running Mrtg To Graph Traffic

May 10, 2010

I am running Redhat linux 8.0 with 2.4.22 kernel. I am using this server for traffic shaping my static ip clients using tc. There are about 250 clients and I am running mrtg to monitor traffic via cronjobs each 5 minutes. When mrtg run I see too much packets loss in my network. What could be the problem in my server?
RAM is 1gb and processor is Intel Pentium D 2.66GHz.

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Networking :: Interface Alias Does Not Receive Broadcast Traffic

Sep 25, 2010

When setting up an alias for eth0, the interface works as expected for normal traffic, but does not receive broadcast traffic.

Host 1's setup:

Code:

Pinging host 1's normal interface from host 2 works as expected:

Code:

Pinging host 1's alias interface from host 2 works as expected:

Code:

Broadcast pinging from host 2 only gets a reply from host 1's real interface (as well as some other uninteresting devices on the network):

Code:

I have confirmed by listening on both interfaces using netcat, and broadcasting using netcat, and again only the real interface receives data.

Is this by design, or is it possible to get interface aliases to receive broadcast traffic?

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Ubuntu Networking :: Slow Network Speed / High Packet Loss

Apr 22, 2010

I have problems with my network speed when i ping my proxy server I end up getting a high packet loss generally more than 30%.I have tried to use various network monitoring softwares like etherape, wireshark, tcpdump but I am not able to get to the bottom of the problem.basically I am trying to find out where the lost packets are going.

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Ubuntu Networking :: Unusual High Outgoing Traffic Generated

Aug 12, 2010

I've noticed recently that a lot of outgoing internet traffic is generated by my laptop (running Ubuntu 10.04 - 64 bit). This wasn't the case previously. I only found out because my wireless broadband traffic allowance suddenly was used up very quickly. I've installed ntop to try to find out where all this traffic is going to.

I did find that there were a very high number (at one stage over 11.000) of active TCP/UDP sessions (see attached screenshot). Although the traffic generated by each is only small (about 100 bits/bytes - not sure what) multiplied by thousands, makes a fair bit of traffic. I wonder if I've got some kind of a virus/bug or do I have a configuration problem with my laptop?

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CentOS 5 Networking :: Configure Firewall - Allow And Forward All Traffic On Eth0 And Block All Traffic On Eth1 Except Ssh Ping

Sep 29, 2010

I need to set up my centOS computer as a firewall in my home network. Ive got 2 interfaces, eth0 and eth1. I want to allow and forward all traffic on eth0 and block all traffic on eth1 except ssh, ping(icmp) and DNS. How do I do this? Ive tried some editing in /etc/sysconfig/iptables but no luck.

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Server :: PPTP Traffic - Gre Traffic Is Being Generated During The Browsing / Reduce Traffic

Sep 27, 2009

Recently I notice that when I'm connected to an vpn server (pptpd) and I'm using it as a default gateway my download and upload speed decreases almost to the half of the usual speed. I made a test using iptables in order to count how much GRE packets are generated (except the real traffic itself) in that way:

Code:
iptables -I INPUT -p gre -j ACCEPT
iptables -I OUTPUT -p gre -j ACCEPT

iptables -I FORWARD -s 172.16.10.101 -j ACCEPT
iptables -I FORWARD -d 172.16.10.101 -j ACCEPT
The first 2 rules match all GRE packets between the pptpd server and client, and the next rules - the traffic between the server and the client.

When I turn the counters to zero and begin to generate traffic (to browse, to download etc.) I see that the GRE packets are even more than these in the FORWARD chain.

So, my question is first of all is my test correct and is it true that so much gre traffic is being generated during the browsing (it becames clear that the traffic is double than if the pptpd wasn't used as a gateway) and if yes - can that traffic be reduced?

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Ubuntu Networking :: Send The Keys Or Value As The Packet Data (content Of The Packet) In Ns-2 (for Wireless Environment)

Jul 12, 2010

I am the new user to ns-2. I would like to know is it possible to send the keys or some value as the packet data (content of the packet) in ns-2 (for wireless environment).

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CentOS 5 :: Update To 5.3 Have Some Packet Conflicts?

Apr 1, 2009

I tried to update from 5.2 to 5.3. But I got the error message:

Downloading Packages:
Running rpm_check_debug
Running Transaction Test
Finished Transaction Test

Transaction Check Error: file /usr/lib/gstreamer-0.10/libgstqtdemux.so from install of gstreamer-plugins-good-0.10.9-1.el5_3.1 conflicts with file from package gstreamer-plugins-bad-0.10.3-8.el5.rf file /usr/lib/gstreamer-0.10/libgstvideo4linux2.so from install of gstreamer-plugins-good-0.10.9-1.el5_3.1 conflicts with file from package gstreamer-plugins-bad-0.10.3-8.el5.rf

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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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CentOS 5 :: Evolution Receive But Won't Send?

Nov 25, 2009

I have it config'd to send and receive on multiple accounts and they all receive email, but SMTP times out and even sends no matter what account I try to send with. I thought maybe security and dropped the firewall and still won't send. No matter which account I try to send to it says its timing out trying access I have no problems on my Mac so no network problems. For grins I install Thunderbird and setup one account and same thing received but no send. What could it be blocking outgoing email??? I have CentOS 5 with all available updates.

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CentOS 5 Networking :: Can't Receive The Multicast Data

Mar 27, 2009

I'm trying to receive data that is being broadcast on address 224.0.1.1, 224.0.1.2, 224.0.1.3, 224.0.1.4. ports are 1201, 1202, 1203, 1204 respectively. I can see the data using wireshark but can not get my program to receive the data. all firewalls are shutdown. iptables is not running, i've set net.ipv4_icmp_ignore_broadcasts = 0 and still no luck.

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CentOS 5 Server :: Can't Send Or Receive Mail

May 24, 2010

My server already installed and works well, but I can't send or receive mail with Squirrelmail, the error that appears is: Server replied: 67 Can not execute command '/ usr / sbin / sendmail-t-i-fteste@gabinetedeengenharia.com '.

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CentOS 5 Server :: Can't Receive Emails - When Primary DNS Went Down ?

May 11, 2011

I'm wondering why we can't received email when our primary DNS went down. We have slave DNS but don't know why we can't receive emails. Internet is working properly. The mail file in /etc/configuration on slave dns are there & the zone file is added. I edited the mail zone file to see if it works & restarted the named service. But still we can't received emails using the slave DNS. Do I need to reboot the server?

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CentOS 5 Server :: Can Send Mail But Cannot Receive - No Errors

Aug 21, 2011

I recently purchased a domain and I have setup what I believe are correct dns records from the domain companies control panel. I have the domain pointing to my server and that's working fine. I also have an MX record for my domain. Now, I can send emails from my email account just fine however I cannot receive any emails coming in to my account. Heres an example:

[dalton@int-interactive mail]$ echo "hello world" | sendmail -v dalton@int-interactive.com
dalton@int-interactive.com... Connecting to [127.0.0.1] via relay...
220 int-interactive.com ESMTP Sendmail 8.13.8/8.13.8; Sun, 21 Aug 2011 14:45:16 -0400

[code]...

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CentOS 5 :: IRC Client - No Traffic Seen At All?

Oct 15, 2009

While I was tweaking 5.3 to get it up to speed on a couple of servers, I used to make some use of IRC 9#centos). Haven't looked at it for a while. Decided to fire it up again tonite, only to find things...have changed. Now there is seems to be 2 channels: #centos and #centos-unregistered. I *was* already registered with nickserv, but that didn't seem to work anymore. Re-registered, but am still seeing no traffic at all. My irc client (chatzilla) suggests there are lots of users 'online', but still - not seeing any traffic at all.

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CentOS 5 :: High CPU Utilization For All Processes?

Apr 9, 2010

I am getting a strange problem with my new machine (P4 3Ghz, 1 GB RAM DDR333). The machine is an industrial PC. Firstly I had installed Fedora Core 2 on it. It ran superbly without any problem. I tried to load Redhat Enterprise Linux WS4 (Update 2 as well as Update 5) on it. But the PC was giving high CPU utilization for each and every task. With-out any application running both the cores shows utilization around 10 %. But when i try to my application, the CPU utilization in one of the cores goes to 100 % for majority of the time. This is causing my appilcation to run slowly when compared to the same application running on the same machine under fedora core 2. (CPU Utilization around peak 17 % in either of the cores in Fedora Core2) Recently I installed Cent OS 5 on it. But the behavior of the PC remains the same as of Redhat Enterprise Linux WS4. Some-where on the forums I had read about the RAM size. So i tried to downgrade the RAM from 1 GB to 256 MB. But the problem remains the same. I think it has to do with some kernel tweaking.

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CentOS 5 :: High Pagefaults In Server?

Jan 19, 2011

I can able to view there is high amount of memory & swap usage on the server, upon investigation found that there are high no of page faults happening on the server more than 300 .. Is there is any option to fix the page faults , and also how to release the locked memory with out using drop_caches..

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CentOS 5 :: High CPU Usage On Clock_gettime() C - C++

Apr 5, 2011

I am calling clock_gettime() function to get time with nano seconds accuracy. My program works fine on Ubuntu but have high CPU usage problem on CentOS 5. it takes 40% CPU on Ubuntu and 90% CPU on CentOS. Kindly give me solution so that I can reduce high CPU usage problem on CentOS. You can build this code like: "gcc -lrt gettime.c -o gettime.e"

[Code]....

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Apr 18, 2011

nstalled Postfix + Dovecot + Roundcube on a plain CentOS 5.5 box, let say on "site.com".I cant send or receive emails. When I try to telnet from both localhost and from the outside world, it can not reach the mail server.Testing itself on port 25:

Code:
[root@srv-estudio:~]telnet mail.site.com 25
Trying 200.40.xx.xx..

[code]...

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CentOS 5 :: Install The Ip_tables Module On A Xen Vps - Receive Error Message?

Sep 3, 2009

I'm trying to install the ip_tables module on a xen vps without success.This is what I've done and the error message I'm receiving:

[peter@sql0 ~]$ uname -a
Linux sql0 2.6.18-128.4.1.el5xen #1 SMP Tue Aug 4 20:51:12 EDT 2009 x86_64 x86_64 x86_64 GNU/Linux

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CentOS 5 :: High CPU Load On Dell PowerEdge2950

Apr 5, 2009

I recently installed Centos-5.3-x86_64 in a PowerEdge2950 machine, to serves as an ftp server using proftpd-1.3.2. I noticed that the CPU load is much higher than the days when I was using RHEL-4.7-X86_64. In the past, CPU load get higher than 100 only when there're about 400 online users. But in Centos-5.3, the CPU load gets higher than 150 when there're 200 users.

The details of the server machine: Intel Xeon E5430, 16 GB RAM, 1.8 TB as a RAID disk, 400GB hardisk used to installed the system.

More details:

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CentOS 5 :: Performance - High Context Switches - When We Run The App, Get This Up To The 500,000 CSs Per Second?

Dec 18, 2009

I have a user complaining about performance:-

Quote: At times on our server, during more-or-less idle moments, context switching is around the 2000-3000 mark.When we run the app, we can get this up to the 500,000 CSs per second. Not only this, but at the same time, the CPUs go to >60% system (the kernel is having to do all that context switching after all), leaving only around 30% for user space. We think it is a possibility that the massive context switching is contributing significantly to our performance issues.

The server is a HP DL580 G5 with 4 x Intel Xeon E7340 @ 2.4Ghz.My issue is that I don't know if the contect switching is a problem or not.From what i've read those values are not necesserilly cause for concern.

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Sep 12, 2011

I am running a CentOS 5.6 32 bit installation under VMWare ESXi and have been experiencing some very high load values from time to time. The server is running multiple installations of gameservers, and the load fluctuates from around 1 to 9, with more or less the same amount of players playing (give or take 5-10 of a possible 80). I've been running DStat with almost all possible metrics, and, except for the large fluctuations in load, nothing else out of the ordinary seems to happen when load is rising. (Log data can be provided, if anyone wants to see it). Disk IO, Network throughput, memory consumption, CPU usage, process count, all stay at the same levels when the load is 1 as when it is 9. How I can begin to troubleshoot this, and find out why the load goes to such high values?

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CentOS 5 Networking :: How To Configure Network For Web Traffic

Oct 18, 2009

how to configure my network for web traffic.Here is my setup:I have the following virtual machines, (all guest are running on CentOS 5.3);

firewall: Smoothwall 3.0, (hardware, not virtual)
guest # 1: Apache http server
guest # 2: Qmail server
guest # 3: Proftp server

I want all of these services on different machines for security reasons, (mainly the ftp server) how do I route the traffic from the firewall to the different machines? I have been looking at setting up a reverse proxy, however, everything that I have read says that a reverse proxy will not handle the smtp/pop3 traffic. Can I just use a DNS server to route the traffic?

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CentOS 5 :: Send Specific SIP Traffic Only Through Tun0-00?

Sep 20, 2010

I got to establish an OpenVPN connection between two server and I have dhcpd on the client server which feeds a few SIP phones. All these phones are supposed to the register server through the tunnel.Here is the network structure:

Client CentOS:
eth0: 192.168.0.0/24
eth1:192.168.100.0/24
tun0:172.15.0.0/24
DHCPD: feeding above eth1 and all the phones with 192.168.100.0/24

If I ping 172.15.0.1 from the the Client CentOS it works all fine. Everything pings and I can even do SSH. However, the phones which obtain their ip through eth1 on the same server can not reach the 172.15.0.1. I think it's a route issue here. Can you please guide me to the right direction as to how to forward certain traffic through tun0 and leave the rest of the traffic to go through eth0?

I don't want to turn on IPTABLES as this is time consuming for me now and there is VPN setup. It has to do with setting up the routing but I am not sure.

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CentOS 5 :: Tunnel DHCPd Traffic Through Tun0?

Sep 21, 2010

Here is what I need to accomplish but somehow not getting where I need:

Server A:
-OpenVPN Server
-NIC1 = Internet (vnet - public IP address)
-Tun0 - 172.16.0.1
Server B:
-OpenVPN Client - Connects to Server A as a Client.

[Code]...

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