General :: No Network Packets Sent Immediately After Quick Physical Disconnect And Reconnect?
Mar 9, 2011
I am using tcp for data transmission between 2pcs running linux.During transmission, I have noticed that if I unplug the network cable and reinsert it quickly,connection is not lost(same as i expect)and the sender start to resend the packet after 5s(what i expect is that network packets sent immediately after quick physical disconnect and reconnect).My question is can i reduce 5s to 0s(resend immediately after network cable reconnect)?Any parameters(tcp rto,txqueuelength,..) can be modified to achieve this condition?
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Nov 27, 2010
i use ppp to connect to a VPN, and i need it to auto reconnect when i looses connection. How do i make it work?I use Debian.
options.pptp settings:
lock
noauth
[code]....
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Mar 14, 2011
I'm thrilled using wicd to connect to wireless networks. But when I suspend my laptop using the special keys, I just want to disconnect from wireless without having to use any kind of GUI or curses user interface. It says in the documentation that wicd works by sending DBUS messages, so presumably it's possible to write a command that talks to the daemon directly.But I can't figure out how.Does anybody know by means of what shell command I can tell the wicd daemon to disconnect me from my wireless network?
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Aug 30, 2010
i need to write a program in c that can sniff packets from Ethernet and distinguish RTP packets from Non-RTP packets, i have no idea what should i do
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Feb 8, 2011
how to fix this error: I wanna compile a C program which niffs the network for arp packets and prints them out ,I keep getting this error:
undefined reference to `pcap_parse' I have installed every thing new version of pcap ,..
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Jul 25, 2011
I have users using Windows XP, Windows 7, Linux (Fedora) and Mac. They all are in a single private network and all access internet through a Linux (RHEL5) system in which Squid acts as gateway. The same is true with my branch offices too except that private network is different and gateway system uses Fedora 9 instead of RHEL5. All the branch offices are connected through point to point leased lines with the head office for file transfer.
My requirement is this: I have a web server located at head office. Presently I am able to access this server from my branch offices through internet. I would like to access this server from branch offices through leased lines. This too I am able to access if I do routing in users system. The file transfer is taking place through one to one system at two ends by creating static routing in those systems.
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Aug 9, 2010
I'm looking for an open source/free network emulator tool that I could use on Mac OS X, to simulate a slow network connection, limited bandwidth and other network characteristics such as dropped packets etc for both UDP/TCP connections (or even on the physical layer).
I'm looking for the simplest solution that would allow me to run TCP/UDP servers and have a few clients connect to them on localhost emulating various network connections. I'm mainly wondering if I can use something like Linux's netem on Mac OS X (or even better cross-platform Windows/Linux/Mac). Perhaps I can run VirtualBox and a Linux kernel running netem, has anyone had luck with that?[URL]...
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Aug 6, 2011
My LAN has 2 PCs installed, Ubuntu 10.04 and Windows XP. I run the server on Ubuntu, and client on Windows XP. Because I am doing stress test, so the client will keep sending tons of packets to server.
The strange thing is: After few seconds, the client program crash because of insufficient network buffer, the server is still ok. But after that I cant connect Ubuntu PC anymore until I restart it. And I check the router, the led for the Ubuntu PC is always ON (not blinking), look like it is jam already.
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Jan 18, 2010
My network connection breaks almost every day. I don't know whose this problem - is it my system or my provider. Everything goes ok until some moment when network disappears and ping my gateway returns "Unreachable host". In that situation I usually plug out cable and plug it in again - now network works.
I wounder if there is a way to do something from console which has the same effect as plugging out/in cable? Or may be more preferred way - can I know what exactly doesn't work when network disappears? What i must repair? May be it save me from reconnecting cable
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Dec 9, 2010
I'm running squeeze testing. I have noticed an issue with the way NetworkManager acts when the wireless connection is dropped. I believe it should automatically reconnect but it immediately puts up a dialog requesting me to enter the wifi password. This dialog stays indefinitely until I intervene and click "OK" (the password from the previous successful connection is still there). I would think that something as basic as wireless networking should not require 24 hour human interaction to stay connected. I have considered a cron job checking the network status and restarting it if necessary, but there is a configuration change or something else I can do to resolve this.
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Jan 6, 2009
Just having updated from SuSE 10.3 to 11.1 I'm struggling with some network issues. WLAN connection setup with Network manager worked, the connection comes up on login to KDE 3 and works for some time. All of a sudden, the wlan connection fails and reconnection via NM is not possible. The normal wired ethernet stays fully operational and connection is established at plug in of the cable. I tried to track the issue down by browsing through /var/log/NetworkManager but I did not find the answer. A rcnetwork restart brings back a fully operational network including wlan connectionvia NM.
Working connection fails, NM fails to reconnect:
Code:
Jan 6 13:04:30 mars NetworkManager: <info> (eth1): supplicant connection state: scanning -> associating
Jan 6 13:04:30 mars NetworkManager: <info> (eth1): supplicant connection state: associating -> associated
Jan 6 13:04:31 mars NetworkManager: <info> (eth1): supplicant connection state: associated -> 4-way handshake
Jan 6 13:04:31 mars NetworkManager: <info> (eth1): supplicant connection state: 4-way handshake -> group handshake .....
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Dec 31, 2010
I have a ppoe internet connection. I was easier and faster to configure it in Yast than in Windows XP. When
The provider here sometimes goes through some problems and the connection may disappear and return at any unexpected moment. In Windows there is a icon on system tray that dysplays such information and I know when the connection is gone. It also allows me to try to reconnect manually. Where do I find these information on Opensuse here do I manage to reconnect. In Windows it was also possible to set the connection to re-dial automatically when it was out. It was very useful if it failed in the middle of a download, the system reconnected and the download manager retried until download resumed. Is there some way to adjust opensuse to reconnect automatically when connection fails or some software that does it? Furthermore, is there a good download manager that works in Opensuse that pause, accelerates downloads and retries when connection fails?
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Feb 25, 2010
use kubuntu 9.10 64-bit on AMD Turion M500 machine.The network keeps disconnecting periodically or on some heavy activity The connection is totally stable on windows 7 though.My doubts point to network manager and so my next step is to switch to command line wpa_supplicant
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Nov 22, 2010
A month ago I had (and still have) a weird problem were leaving my switched off computer plugged into the network killed the whole network.
[URL]
well I have found a fix, if I disconnect my computer via software (Right click and disconnect "eth1" and shut down the network will remain up. I want to make a script that runs on shutdown that simply disconnects "eth1". Are there any pre-made shutdown scripts in ubuntu that I can simply add "eth1 enabled = 0" or something.
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Jul 19, 2011
i installed linux at home on my laptop (dv2000, hp). Because i was having problems connecting to the internet through wireless. And wired at friends houses.So installed linux. Wireless took me a while but finally got that working. Now the problem i have is that wired is not working apart from at home. Any other router apart from mine it cannot connect to.
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Sep 28, 2010
I installed Red Hat Eterprise Linux 5.4 Server on my HCL Server machine.I use a static IP for my server. The problem is the network connection is automatically disconnected for some times and it again connected automatically after some time. It happens in periodic manner.I check my cable, port and connection.Those works fine in other PC
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Apr 2, 2010
The main thing preventing me from going Linux although I have it installed in a multi-boot is the probelm I have with Reconnecting the Network (eth0)
If I reboot everything is fine and I am automatically connected to internet via my Ethernet_NAT_router/Homeplug_PowerLine/Cable_Router (using DHCP)
But if I manually disconnect the Network using the tray icon, or through the terminal, when I reconnect the Network Manager says I am reconnected but actually I am not connected to the internet. I can load my Cable Routers configuration page but pages beyond that in the outside world are accessible no longer...
To regain access I have to reboot.
The reason this is important for me is that I reckon if I could get this sorted then if I put the laptop to sleep it will will wake up and reconnect.
As it is using Linux sleep function is unworkable unless I don't mind losing internet.
I am determined to get this sorted eventually as I feel sure there must be a solution. My laptop isn't new but is a good workhorse.
Dell Inspiron 4100 / OpenSUSE Linux 11.2 Gnome
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Oct 1, 2010
I've been experiencing one issue in my opensuse 11.3 KDE, the thing is when leave my pc downloading a file, it disconnects after a period of time, I don't know when exactly. I connect to internet at boot time via DSL modem, when I was setting up my connection I noticed, that there is an option "idle-timeout" I set it to zero "0", I know that my pc donwloads all the time and speed do not drop, why then it disconnects?, it disconnects even with higher numbers of idle-timeout. It happened on the other laptop too, so I need every time to "rcnetwork restart" to get it back working
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Jul 31, 2010
I recently installed Ubuntu 10.04 on my Acer TravelMate 3270 notebook (with Windows 7 dual boot) for everyday use. All is great except i started to notice my Wireless Network get disconnected and then reconnects every 5 minutes or so. Also the NetworkManager Applet 0.8 keep annoying me with the notifications that its disconnected and then reconnected.
I do not have this issue while using Windows 7 (in the same area). Can this be fixed. As i really want to move my day to day computing need to Ubuntu.
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Feb 8, 2010
i have a linux server runnig oracle applications. i need to access this server from putty using ssh through internet. i did by registering my static ip with the dnydns.org and i am able to connect to the server. but now there is no security to authenticate any user as any one knowing the password can login to it.
i thought of configuring the firewall of linux server but the client ip`s are not static and they change continiously. so thought of keeping one more pc between the server and the router which will do the work of authenticating. but i am confuse as how to configure it to allow the packets coming from the internet after authenticating and to by pass the packets generated from internal LAN?
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Aug 8, 2010
I created a similar thread last week in the networking section but only got one response. I was hoping to get a little more help here as this forum helped me tremendously to partition my hard drive safely. That was over a week ago, and ever since then I have been struggling with setting up my network. Here is what I have done.Basic set up with netconfig. I selected DHCP and followed the directions on the screen.ifconfig -a shows eth0 with no RX or TX packets at all, but at least it showed me information. If it was not detecting my card (which is compatible with linux), it would have said no device found. correct?
dhclient eth0 just hangs there for half a minute until I can add a command again.dhcpcd eth0 times out.I read (in slackbook chaper 5.2.1) that the correct kernel module may not be loaded. So I opened rc.modules with pico and went to the netdevice section. In slackbook it said to find my device and uncomment it.... but I cant find it! (I have an atheros ar9285 in my stock compaq CQ61 laptop) I also opened rc.netdevice and it was empty..It seems like the more I learn about the network, the more lost I get. I keep hearing that configuring a network on slackware is easy, am I just missing some simple step?Also, whenever I startx, akonadi gives me an error. I also get another error saying that it could not parse XMS file. Is that just due to my lack of an internet connection at the moment?
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Dec 10, 2008
I am not a networking expert by any means (in fact I have never taken a networking course), but I have taken several security courses, and generally we wind up discussing replay attacks. For example, the Needham-Schroeder protocol (using symmetric-key cryptography anyway) is flawed because it allows for replay attacks, and I understand why.
I guess my question is actually how someone would perform a replay attack. I know I can sniff network traffic by downloading wireshark. I also have downloaded winpcap and npg on my WinXP virtual machine. I'm trying to use this guide to help me, but I'm quite lost:[URL]What I did was to post a "link" to my facebook profile and I sniffed the traffic using wireshark. What I would ultimately like to accomplish is to copy that packet out of the wireshark output, and then use a tool like npg to transfer the raw packet back to facebook, which should result in a second, redundant post. I just can't figure out how to do that.
I'm pretty sure this should be possible. Facebook only uses an SSL session for authentication during login. After that, the information is just sent in the clear, so I'm pretty sure this should be possible.Can anyone explain how to do such a thing? It would really help my research paper that I'm working on this semester if you can. As of right now the attack we are trying to demonstrate/defend against is using a Windows VM, which is why I'm using winpcap/npg. The attack is actually possible using just about any OS (depending on the exploit used), but our POC is Windows only at the moment
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Feb 15, 2011
I'm using madwifi linux driver (ath1) in monitor mode to capture some wireless traffic. I can see that all wireless traffic is coming well through the wireless interface (checked using TCPDUMP). What I want to know is how I can forward the captured wireless packets to a different Ethernet interface (e.g. eth2) in the same machine to send those captured packet out to a different computer.
I set 1 for /proc/sys/net/ipv4/ip_forward
for iptables, I tried this rule: iptables -A FORWARD -i ath1 -o eth2 -j ACCEPT
However, I coudn't read any packet from eth2 via TCPDUMP.
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Feb 17, 2010
I am running into trouble while trying to set-up a iptables routing policy. I have two machines on the same sub-network (xxx.xxx.153.0). One of the machines is used as a default gw for the other (xxx.xxx.153.250 is a gateway for xxx.xxx.153.142 and xxx.xxx.153.254 is a gw for xxx.xxx.153.250). There is no explanation for why the xxx.xxx.153.250 is in the middle -- xxx.xxx.153.142 can go straight to xxx.xxx.153.254, but is is like that for now.I am trying to find an iptable rule to be executed on the xxx.xxx.153.250 machine to route the packets.
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Jun 3, 2010
Centos el5xen x86_64 in a company network, novell-netware, Static IP I have several issues with the Xen network configuration. This configuration worked before, and was maded by a other personn with a higher level in centos and network . I'm trying to re-install xen in bridging mode.
1) The dom0 ping in the company network, but can't acess to the Internet.
I de-activated firewall, iptables and SE-Linux for the test.
the ifconfig-a command return
eth0
lo
sit0 (IPV6 encapsuled in IPV4)
vif0
vnet0
but no Peth0 Physical device
Is it normal and how can i repare this ?
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Mar 27, 2010
I am using vnuml to test a network project. I have one Ethernet card on my ubuntu 9.10( eth0) with network 10.1.0.0/16, and creating a tap0 with subnet 10.4.0.0/16. Now the problem is how to work them together, such that packets from one interface goes to other one?
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Jun 27, 2010
For some simulation, I am trying to configure a setup of 3 ubuntu desktops (one of them with multiple network cards) to behave in the following way:
Each one of them should be a separate network not seeing the others (including multicast addresses) They need to have internet access through the machine with multiple network cards. So from the point of view of each machine they define a LAN in which it is the only device and have internet access through the gateway machine.
What do I need to do to configure these machines for the above setup?
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Feb 10, 2010
I have a small network with 4 users, a Win2003 server for LAN/security functions, and a Dell Blade server running Ubuntu 8.04.1 which runs as our web server on port 80. I manage the Ubuntu server with Webmin v1.42Yesterday, my users weren't able to access the internet nor were they able to receive mail, etc. and no one could access any of the website hosted on the webserver. However, the internal users could access each other's PCs and internal printers and devices - just nothing outside.
I began to troubleshoot: I could see a lot of activity on the Router/Firewall on the port connected to the Ubuntu server. When I unplugged the server, everyone could immedately connect to the internet. So, the problem was originating with that server.When I logged in to the Ubuntu server using Webmin, I checked System>Running Processes and right at the top of the list was the process:ID Owner CPU Command23184 www-data 98.1% ./s 174.120.164.186 7777When I drilled down on this process it said that the parent process was:/bin/sh -c ./s 174.120.164.186 7777I pressed the Trace Process button and it appears to be sending the following repeatedly:Time System Call Parameters Returnxxxx send 125,0123456789ABCDE,15,0 15So, I manually Killed the process and added a rule to my firewall/router to block an IP range that includes 174:120:164:186
A few hours later the same process stars again in Ubuntu,, effectively plugging up my pipeline to the internet and preventing access to the websites being hosted.It suspect that there is some kind of virus on my Ubuntu machine but have no idea how to locate and destroy it. I am relatively new to the Ubuntu world and would appreciate anyone's help immensely! I just don't know what to do!
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Feb 7, 2011
I'm sniffing network packets in ubuntu, I need to write these packets as raw bytes to memory but libpcap give packets in its special format. how can i save and recover packets in byte format?
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Apr 7, 2011
I want to simulate a wireless network where all nodes broadcast packets
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