Networking :: ICMP Got Lower Priority?
Mar 16, 2010
I run a linux box as a gateway behind a satellite modem. The internet link over the satellite modem is only 1mbit so the usage often reaches 100% when someone is downloading/uploading something. I am seeing my ping return time jump from 700ms to 6000ms if someone tries to upload a file (by sending a attachment in a email etc). The satellite operator is saying this is normal, but I have my doubts.
Has ICMP got a lower priority? Should I really be seeing this behaviour? I understand that if it was a TCP packet then it would just be queued until the previous acknowledgement has been received. And if it was a UDP packet then it would have been dropped, but how does ICMP deal with these situations during heavy traffic?
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May 12, 2011
I'm trying to dump a mysql database on a small web server without killing performance. I tried using the nice command to give the mysqldump and gzip a low priority, but gzip is still taking up 100% CPU. Pages on the web server are loading incredibly slow. Here's my command:
Code:
nice -n 19 mysqldump -u USER -pPASSWORD DATABASE | nice -n 19 gzip -9 > OUTFILE.sql.gz How do I get gzip to run without taking up 100% CPU? I've attached a screenshot of top about 8 seconds into the dump.
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May 21, 2011
I am setting up a virtual server. Ubuntu 11.04, "minimal provider image".UFW was disabled by default. I set it to default deny. Allowed HTTP, SSH and other standard stuff, and enabled it. All seems to be OK. Adding one rule to block some annoying security scanners causes ping not to work. I'm not an Iptables expert, but it looks OK to me. I got it from some website, rather than invented it myself, but modified to to fit the ufw config file syntax. What in that rule prevents pings?!? It seems completely unrelated.
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Dec 9, 2010
I have BT4 as an iso image and start it up by booting from cd, when i try the command root@bt~:startx it comes up with this fatal error. what can i do to get this work? and of course im new at this.
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Mar 12, 2010
I tried to add my wife , and when I put in a password for her, this error comes up."Please set a valid user name consisting of a lower case letter followed by lower case letters and numbers." I did all that and I still can't set a password for her.
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Dec 1, 2010
how to identify the icmp packets & marking. this below icmp packets marking is not working.
iptables -t mangle -A PREROUTING -p icmp -j MARK --set-mark 0x5
iptables -t mangle -A PREROUTING -p icmp -j RETURN
with the help of port no or any other how can i identify the icmp packet ?... This below two is working fine
iptables -t mangle -A PREROUTING -p tcp -j MARK --set-mark 0x2
iptables -t mangle -A PREROUTING -p tcp -j RETURN
iptables -t mangle -A PREROUTING -p udp -j MARK --set-mark 0x3
iptables -t mangle -A PREROUTING -p udp -j RETURN
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Feb 20, 2011
Is there a way to set the IP that's returned in an ICMP TTL exceeded packet? Reason I ask is I have an edge router with several upstreams, and several downstream routers, and when I traceroute to it I would like only one of it's IP's to show up in the trace (Instead of each . Much like some of the larger ISP's do to mask the IP and hostname of their internal routers.. Is this possible?
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Jan 12, 2010
I have One Server which is having IP 10.176.0.155. I want that client 10.176.0.135 is not able to ping this server only & cane it is possible to block through hosts.
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Jun 22, 2010
Why linux traceroute uses UDP protocol, we have basic ICMP protocol which is used in MS-windows tracert.Any specific use of traceroute using with UDP,TCP than ICMP?Windows is displaying all HOPs address but linux printing *.*.*
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Jul 9, 2009
I have a C program which does.
1. Creates a UDP socket
2. Send the UDP Request packet to the TFTP server.
3. If the TFTP server is not listening in the 69 port, the remote machine send an ICMP ("Port Unreachable") message.
Is there a way to receive a notification from the Linux kernel on receipt of an ICMP packet to the created UDP socket.
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Aug 19, 2010
icmp request from an ip that is in the same network as one of the local interfaces is not responded to, if the ping request is received via an interface in a different network. Is this some security feature?
Consider the below network
x.1|RTR1|-y.1---------y.2-|RTR2|-z.2------z.3-|LNX|-x.3
RTR - Router
x.1 -> 192.168.x.1
LNX - Linux machine
[Code]....
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Jul 23, 2011
So im trying to get an icmp tunnel setup using ptunnel. When I run it under the same network and use to connect to RDP, it works fine, however when go outside my network and connect in, it does not get anywhere. I can confirm that I have forwarded ICMP packets to the server (if I ping the external ip it will show the status of the server if I unplug it) and that the server is showing signs of registering it.
On the client it just tries to resend the packet "Resending packet with seq-no 0" Over and over Firewall is off for testing so thats not the issue.
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Sep 10, 2009
From what I've read, when linux sends a ping it sends without the netmask, so windows server assumes it must be a broadcast? Why doesn't linux send a netmask with a ping?
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Nov 13, 2010
I tried to ping some of the pcs on the local network but for those with icmp disabled it doesn't work. I've used
Code:
nmap -sP 192.168.2.0/24
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Jan 8, 2011
Installed Ubuntu Server 10.10, included Apache, PHP, and OpenSSH. Apache is up and serving pages, I can connect using PuTTY no problem. Server responds to a pingHowever, attempting to use ping or traceroute from the server results in a Destination Unreachable. Happens even for other 192.168.1.10x boxes on the local network
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Feb 8, 2011
Why firewalls does not allow ICMP echo request packets. Why are pings not allowed to certain systems?
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Apr 21, 2010
Can any one tell me a network monitoring tool which can monitor remote connectivity and generate a comprehensive report about the link state like up/down, error timings, increase in latency and packet loss rate.
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Feb 21, 2011
On my system, I have built my own tunneling protocol, where I relay packets over a non-standardized but verified medium. What I do is capture the packets using iptables and NFQUEUE, relay them over my medium, and at the other end I reinject them using raw sockets. The packet going into the tunnel is exactly the same as the one coming out, verified. The problem is that this doesn't work for ICMP Ping (Echo Request) if the destination of the ping is the same as the tunnel endpoint. If the destination is not the same as the tunnel endpoint, the ping packet is rerouted and arrives as it should at the receiver, and the ping reply comes back to the sender. Does anyone know whats going on? Isn't it possible to send raw icmp to yourself? If not, anyone have an idea what I should do instead?
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Jan 19, 2010
how can i set boot priority of the os through grub on ubuntu system on my laptop.
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Jan 14, 2010
I set up a static IPv6 address and a gateway in /etc/network/interfaces. However, a bad router in my network environment alway send wrong ICMP router discovery messages to me. So I have got extra (wrong) IPv6 address and gateway, and the routing is confused. On Windows Servers, I can use "netsh interface ipv6 set interface "Local Area Connection" routerdiscovery=disable" to disable ICMP router discovery. But I don't know how to disable it on Ubuntu 9.10. How could I disable ICMP router discovery for IPv6?
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Sep 28, 2010
When I ping our Microsoft Windows terminal server "cluster" farm, I get ICMP warnings that there are duplicate packets. I am able to rdesktop to the cluster with no problems. We are trying to setup nagios to run on this Ubuntu configuration and nagios is reporting the following error:
"PING WARNING - DUPLICATES! Packet Loss=0%, RTA=.98ms.
FPing reports duplicates as well. Is there a setting in the Arp table that needs to be set differently because the "Cluster" MAC address isn't an actual hardware MAC but a virtual MAC address?
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Mar 9, 2011
Struggling to get my Linux server accept ICMP redirects not originating from default gateway. No problem to get it working if the redirects is originating from def gw.I know it's not a good solution security wise, but my network is so cluttered I'm forced to do so.
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Apr 20, 2011
I have a dedicated host on my lan to monitor other hosts/services using Nagios. I'm in the process of migrating to Zabbix on that host to perform the same purpose. Both Nagios and Zabbix monitor icmp ping latency (Nagios uses ping, Zabbix uses fping) and over time the latency to other hosts grows until threshold alarms are triggered. In one week, the average latency grows from sub-millisecond to over 100 milliseconds, and continues to grow until the Nagios host is rebooted. I have verified the latency numbers using ping/fping from the command line on the Nagios host.
The problem is that pings from the monitored hosts to the Nagios host show normal latency at the time the Nagios host is showing high latency from itself to the monitored hosts. The Nagios host and monitored hosts are all connected to the same Dell 24 port gigabit switch. I already posted this question on the Zabbix forums with a graph of the latency but there were no answers. [URL] why the icmp ping latency is growing over time and how I can fix it short of rebooting the host on a schedule.
[Code]...
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Jan 25, 2010
In my network my proxy / firewall (iptables + squid) works as dns forwarder. I needed to configure an url at my /etc/hosts in my linux boxes which are behind the firewall into the lan. I want my machine to look at its local /etc/hosts file before querying the dns to the firewall.
Despite I configured my /etc/host.conf this way:
My machine keeps resolving the name through the dns forwarder (firewall) and not from the /etc/hosts file first.
Is there any action needed after configuring /etc/host.conf? Any service to restart?
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Jan 9, 2011
I installed 10.04 1st by making a partition with bootcamp on MacOSX.Then I formatted the partition according to Ubuntu's instructions. I didn't install rEFIt, because I prefer to just hit the alt (option) key.I made the necessary adjustments according to URL...Community Ubuntu Documentation - and everything seemed to be working fine.I upgraded to Maverick and everything seemed to be working fine aswell.But then I noticed, that the wireless signal keeps failing and I'm asked to put the password again and again..
I don't think this is due to the upgrade from 10.04 to 10.10, but I just noticed it recently, maybe because of the air humidity, the signal was stronger a few days a go.. don't know!!Is there anything I can do?Perhaps install a new driver, or another wificlient, like Wifi-Radar??
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Apr 19, 2010
Why is wireless taking priority from the wired connection? I should not have to disable wireless just to have the wired connection connect.
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Sep 26, 2010
I've got two network card interfaces on my computer, one wireless and one wired. The wireless card is connected to the Internet and the wired is connected to the LAN. When only the wireless card is active, Internet works. As soon as i enable the second wired card, Internet stops working. And it seems like Ubuntu chooses the wired card for Internet as soon as it's enabled.
Are there any ways to solve this? So my Ubuntu box always chooses the wireless card for Internet traffic and let me use the wired device for LAN only?
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May 9, 2010
I am encountering a wierd problem in FC12. When I try to lunch a program that listens to a lower port such as 80 or any one that is less than 1024, I always get "Permission denied" error message (I am running it as root!).Then I try starting httpd service daemon that listens to 80, no errors, the daemon started and listend to 80.PS: I checked selinux, it has been disabled.Do you have any knowledge on this case? BTW, the kernel version is:2.6.31.5-127.fc12.i686.PAE #1 SMP Sat Nov 7 21:25:57 EST 2009 i686 i686 i386 GNU/Linux
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Sep 30, 2010
I am a noob in Ubuntu and I would like to create and script or file which when clicked sets my WiFi interface's power lower, down to 7dBm. I already know how to do it by typing on the terminal, I just write:
#sudo -s
#my password
#iwconfig wlan0 txpower 7dBm
[code]...
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Nov 12, 2009
I want to block the icmp packets(ping) from the other computer to my RHEL-4 what's the syntax I should use to do so in IPTABLES.
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