UDP stands for User Datagram Protocol. With UDP applications can send messages (datagrams) to other hosts on a network without requiring prior communications to set up special transmission channels or data paths.

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Firewall UDP Flood Dos/DDoS

Recently I have been suffering from what appears to be a UDP query flood attack. I am looking for a way to block the attack using a software firewall such as iptables, this should be possible, as ...
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68 views

I need to REJECT first incoming UDP packet by srcip

Im currently under attack by spoofed udp packets. Every spoofed ip trying to send just 1 udp packet in 30sec. But there is tons of ip. I need to drop first packet. But if same srcip in 30sec sends ...
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172 views

Blocking ddos string with iptables [duplicate]

I want to ask how do block spefic packet payload? 14:46:35.837759 IP 145.92.16.14.27017 > x.27030: UDP, length 25 0x0000: 4500 0035 44a4 0000 ee11 53ae 915c 100e E..5D.....S..\.. ...
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51 views

Dest host dont accept UDP when there is no route to source

I have three hosts with following config: Host A: IP:192.168.1.1/24 Host B: IP:192.168.1.2/24 Host C: IP:192.168.3.1/24 Everything happens on CentOS 6, and all interfaces are VLAN tagged (if it ...
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1answer
257 views

How to kill a UDP connection from a process Windows Server 2003

I have a program running and it connects to a UDP port to perform multi-casting. I'm trying to simulate a network failure where that process cannot reach the UDP endpoint but everything else still ...
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937 views

Enable UDP protocol in Remote Desktop Connection

I have a computer to which I am connecting via RDP. However, using the default Windows applications (Remote Desktop Connection) probably will not use UDP port. By clicking the connection information ...
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1answer
255 views

Sending file with netcat over UDP: Unusual Wireshark output

For the purposes of demonstrating differences between TCP and UDP, I'm piping the contents of a file across a network connection, and recording the interaction with Wireshark. Everything looks normal ...
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1answer
189 views

How to tunnel UDP traffic with pptpd VPN?

I've set up a VPN on a Debian (7.8) server. On a Windows 8 machine, I can set up a VPN connection to the server and it works fine for TCP applications. Everything is going through the VPN. However, ...
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12 views

Route only on output chain?

I have two machines A and B. I want to send iperf traffic from A to B, but first have it route through a userspace program on A. I did this with a tunneling device: therefore, I used the command ip ...
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1answer
139 views

iptable rule and iftop command

Someone is flooding our server with UDP packets. I simply put iptable rule to block that IP. However, when I run iftop command I can see a huge traffic coming to my server. When i looked for iptables ...
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1answer
815 views

socat udp packet forwarding with source address

I am trying to use socat (instead of iptables) for UDP port forwarding. I just need to redirect some traffic from UDP port 162 to 33162. I am using something like this: socat udp-listen:162,pktinfo,...
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2answers
288 views

Can't change source IP address (to floating ip) for udp outgoing packages

I'm having trouble getting a cluster to work using pacemaker and corosync. Here is my hardware configuration: Network: 192.168.3.0/255.255.255.0 Gateway: 192.168.3.1 node1 (Ubuntu Server 12.04 x64) ...
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20 views

Can't stop the UDP packets [duplicate]

My datacenter has stopped my cloud server because my server is producing excessive UDP traffic. I have run: tcpdump -i eth0 udp and following is a sample set of log. 13:09:42.789583 IP mobile-166-...
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1answer
102 views

Caching UDP packets with iptables

I have a server set up to forward all of its packets on a certain port to another host with the following command; iptables -t nat -A PREROUTING -p udp --dport PORT -j DNAT --to-destination IP:PORT ...
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1answer
212 views

heartbeat timeout error in tsunami deamon

I am trying to transfer a large file from server A to server B using tsunami. I am getting following error: Heartbeat timeout of 15 seconds reached, terminating transfer. And here are details: ...
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1answer
297 views

Vendor whitepaper says: 5Mpps no prob. I'm already hitting a wall at 120kpps. Where's the bottleneck?

HP's whitepaper on their QLogic (fka Broadcom) NetXtreme II adapters, which includes the specific NIC that I'm testing, states (page 7) that their small packet performance for packets up to 256 bytes/...
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1answer
49 views

How does acting as an RDP host affect UDP visibility/routing?

This is an odd one. First, THIS IS NOT A NETWORKING ISSUE. This is an "rdp host behavior" that can be seen, from one persective, via the behavior of an RDP app. (see What happens to a Windows 7 ...
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1answer
2k views

Block an IP for UDP

I am under UDP flood attack. I used following protections to solve it: iptable IP ban: iptables -I INPUT -s 37.187.231.xxx -j DROP Tried another iptable syntax /sbin/iptables -I INPUT -i eth0 -s ...
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2answers
6k views

Extreme UDP packet loss at 300Mbit (14%), but TCP > 800Mbit w/o retransmits

I have a linux box I use as the iperf3 client, testing 2 identically equipped Windows 2012 R2 server boxes with Broadcom BCM5721, 1Gb adapters (2 ports, but only 1 used for the test). All machines are ...
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1answer
337 views

Make Asterisk to serve another subnet

I have server with Linux Ubuntu 12.04. It has two subnets - 192.168.0.1(eth0) and 192.168.1.1 (eth1). There is an Asterisk server (IP PBX) connected to first subnet, lets say it has IP address 192....
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4answers
569 views

tcpdump increases udp performance

I'm running a set of load tests to determine the performance of the following setup: Node.js test suite (client) --> StatsD (server) --> Graphite (server) In short, the node.js test suite ...
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563 views

Fast Ethernet UDP optimize receive buffers

I have a Linux computer which must receive streaming data from several devices (up to 30 or so) during long terms. This computer is connected to a Fast Ethernet local area network (100 Mbps) where ...
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1answer
50 views

How does udp work when links en route have different speeds? [closed]

My understanding of UDP is that it is a best effort protocol. The data is simply sent and may or may not get there. If I am sending data from A to B using UDP over the Internet and the first link ...
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242 views

Multicast works only in promiscuous mode

I'm trying to receive MPEG-TS over UDP multicast transport in Arch Linux. So when I run ffprobe -i udp://@224.1.1.240:6000 it hangs forever with no result. Then I run tcpdump and it shows no ...
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1answer
348 views

How to setup routing for UDP in AWS instance

I'm new to AWS and I'm wondering if any one could provide a guild/link on how to go about setting up, what I'm guessing is VPC, so that I can send UDP packets to and from my instance via my public IP. ...
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1answer
110 views

Monitoring /proc/net/udp

I am interested in tracking changes in /proc/net/udp, particularly in the "drops" column. I want to know the the approximate time when a drop counter goes up. Also, if the socket gets destroyed, I ...
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67 views

RX errors when using jumbo packets

We have a device outputting high speed data over UDP connected directly to a processor (no switch). The processor is running CentOS 6.6. The connection is gigabit Ethernet. When we use packet sizes ...
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1answer
2k views

Why some iptables DNAT rules don't work until reboot?

My iptables DNAT rules don't work until reboot. If I reboot my server, all of the rules work. Desciption of the architecture : Tens of hosts (senders) send some UDP packets (one-way on a specific ...
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2answers
6k views

Load Balancing DNS Servers: UDP / TCP

I have been asked to rebuild our load balancing infrastructure in the data center. The original request was to load balance FTP servers. I tried doing that using the current load balancer (Piranha / ...
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1answer
158 views

Multicast and duplicate IP addresses

I've developed a Multicast UDP client/server application, which allows a user to remotely change the network configuration of devices belonging to the same multicast group. But what if a device was ...
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373 views

Piping device file over UDP with netcat

Hopefully this is the best Stack Exchange site for this - I think it's primarily a netcat question. I'm developing a custom data acquisition device. It can probably be best thought of as a fancy ...
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1answer
1k views

UDP reverse proxy on Linux [duplicate]

I have a dedicated server which hosts game servers, and is vulnerable to DDoS attacks. I want to get a DDoS-protected VPS to act as a reverse proxy for UDP. The dedicated server's IP address is 7.7.7....
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1answer
366 views

Maximum size of empty UDP packet

I want to stuff data into a packet, but I want to make sure that the packet does not exceed 512 bytes, so I need to know what the initial size of a UDP packet is so I know how much data I can put into ...
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190 views

Does Ubuntu with Linux 3.5 having TX RX ring buffers or BQL

My linux uname -a command outputs: Linux Davinci001 3.5.0-23-generic #35~precise1-Ubuntu SMP Fri Jan 25 17:13:26 UTC 2013 x86_64 x86_64 x86_64 GNU/Linux So, does NICs with this Ubuntu machine is ...
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1answer
259 views

Is Linux limiting my application's UDP transfers, and how can I see it?

I am currently developping two applications to work over a custom video streaming "protocol". Basically: The server captures video frames from a webcam, slices them into parts, and sends these parts ...
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1answer
209 views

Plain UDP shows up as STUN in Wireshark

I am sending 4 bytes of data over UDP upon request from another program. Sometimes the frame's protocol is identified as STUN in Wireshark, but I have no clue why. A ruby prototype of the ...
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1answer
252 views

Is ARP Connection oriented or connectionless?

Is ARP Connection oriented or connectionless? It uses TCP, but does that consider it connection oriented?
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103 views

Redirect packet that matches a pattern?

How can I route an incoming udp packet with iptables that matches a pattern like: 53 41 4D 50 5B 79 95 DB 61 1E 69 from public interface (vmbr0) and port 7777 to 192.168.0.1:7777?
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2answers
855 views

tcpdump truncates to 1472 bytes useful data in UDP packets during the capture

I am writing an application which work with network. To perform some tests I need to reproduce the flow which I had a day before. But at the same time it is not allowed to stop the current working ...
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1answer
198 views

How to drop first udp packet from a source with iptables?

As a defense against distributed udp flood, I need to drop first udp packet from a source and accept other than first packet. Does iptables has capability of doing this? If yes, how?
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306 views

Would UDP over VPN eliminate packet loss?

I am receiving a MPTS UDP stream from a remote location and I am experiencing packet loss. I would like to know if there's any way to eliminate this packet loss while still using the UDP protocol? I ...
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1k views

Linux: Reduce UDP Packets Error

I'm facing UDP packet receive errors (under Linux 'netstat -su' command). I have 10 x UDP processes running on Machine-A (RHEL 5.2) and each of them send 290-byte packet at 50 times per second to ...
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2answers
123 views

Clients phone provider claiming high latency over UDP, how do I test?

A client of our uses a hosted phone solution for his 50 agent call centre. They use a hosted dialer who make the out going calls, once the connection is made the call is passed to my clients user ...
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2answers
312 views

TCP/UDP Small Package Size optimization [closed]

I currently have the problem, that when a LOT of RTP streams (>800) go to one server the max. speed is onlynabout 70-80 Mbit (on a Gigabit LAN - all Hardware components are Gigabit components) 130 ...
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111 views

How can I log and maybe even block IPs that send lots of incoming UDP traffic?

we run a voice / teamspeak server which receives legitmate traffic on port 9987 from many ips. Sometimes we get DDoSed. So people use single Servers and send 1-3 Gbits of UDP Floods to that port. This ...
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1answer
832 views

UDP Proxy with cloned packets

Having UDP messages sent from dynamic public IP periodically to public IP X:20000. Need a proxy that listens in IP X:20000, then forwards duplicate/clone packets to X:20001 and a different machine ...
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93 views

How to turn a UDP feed on and off?

I have a linux application that is sending a stream of UDP packets to a particular ip and port. I need a way of suppressing this packet stream so the packets never reach the network, with the ability ...
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2answers
385 views

NAGIOS host availability test for host that can't be PINGed, won't talk to me, but can be traceroute'd

Part of my network estate has a fairly important dependency on a host whose availability is difficult to check. I have a number of hosts behind it, and my NAGIOS VPS provider occasionally has routing ...
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1answer
589 views

Netcat UDP File Transfer Between Two Servers Times Out?

I'm testing file transfer speeds between two Red Hat servers that are connected to the same switch within the data center and I decided to use netcat to eliminate protocol overhead as much as possible....
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2answers
3k views

lots of UDP_IN Blocked errors

Since I have reinstalled my OS, I'm getting lots of UDP_IN Blocked errors in my messages log. Can anyone kindly explain what the error say exactly and what I can do to get rid of this error. Aug 8 ...