Packet Flooding ...
May 8, 2009
I have been faced with a packet flooding issue.
Quick scenario, I run a few public game servers, and we have had a member go insane.
This member has been using a piece of software, to do a simple DDoS attack, and when they perform this attack, it laggs everybody out, and takes down the individual game server.
While this is occurring, I have been watching with a network analyzer program, and noticed the packets go sky high (from 4.4k to 150k+).
So, I am in need of a quick, piece of software that can block flood attacks, or whatever is going on.
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May 13, 2008
Well I've tried Staminus and Awknet and they both just seem to rate-limit if I get like 300MBIT SYN, is there any provider that won't just rate-limit but will actually filter the attack for around $200/mo?
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Aug 15, 2007
my new server performs strange
I checked /var/log/messages
there are full of these messages
possible SYN flooding on port 80. Sending cookies.
kernel: printk: 84 messages suppressed.
kernel: nf_conntrack: table full, dropping packet.
my site is a huge site, thousands of ppl online
I think i am not been attacked, but kernel think so.
How to resovle this problem.
How can I stop netfilter from kernel
kernel:@2.6.22.1-32.fc6
2 xoen 2.8g, 2gb ram, 73gb scsi hd
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Apr 12, 2009
My website has been under a constant Syn Flood DoS attack for the past few days. However, the attack originates from a single IP address that changes every few hours (Possibly a syn flood script with IP spoofing capabilities).
The Syn Flood attack isn't creating any spike whatsoever in my usage graphs, however, its still rather annoying. What firewall should I use to combat the DoS attack?
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Aug 15, 2007
Someone seems to be flooding our HTTP server somehow. We use the latest version of Apache on Windows.
Is there any Windows modules that can filter the total amount of IP connections, or something built into Windows that could filter this?
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Jul 21, 2007
I made a thread about this in programming as I was trying to figure it out but I ended up tweaking dos deflate a lil and got it working. Tried and tested as well during low bandwidth syn flood. Keep in mind if you are having massive syn attacks then most of it will have to be filtered on the network level. I have filtering from staminus on my server, this is just for the low bandwidth stuff that gets through.
Syn-deflate is just a name I came up with as it is based on dos-deflate, only a few changed features. I dont know how medialayer would feel about me modifying their script this way I know they got lisence and copywrite on it. Guess I will talk to them about that before any official release.
especially about the csf version.
So I always have used some dos deflate features to monitor dos in my servers, just the netstat command. This one:
Code:
netstat -ntu | awk '{print $5}' | cut -d: -f1 | sort | uniq -c | sort -n
Today, got a syn flood coming through, low bandwidth, etc. Each ip connecting under the tracking limit for csf. So I tweaked the netstat command a lil bit and I was able to see what ips were sending syn and how many times.
Like this:
Code:
netstat -ntu | grep SYN_RECV | awk '{print $5}' | cut -d: -f1 | sort | uniq -c | sort -nr
So I figured it would be very handy to ban ips sending over so many SYN_RECV connections at once. So I took dos deflate and tweaked it a lil. Made this to work with csf. Only problem on csf is there is no unban command, only whitelist so I just had it do csf -d again on the unban command, This would give an error and would not unban the ip but you really dont need to unban it so soon.
With apf it works perfectly on unbanning. Works just like dos deflate but bans syn flooders not connection flooders. You could even use this along with dos deflate. I am using it along side of csf and the connection tracking feature no problem.
I plan on releasing some what of an official version too along with some other tools to monitor and stop dos. So whoever is interested or can offer some advice let me know.
For those who wanna give it a try:
For the CSF version:
To install:
Code:
wget[url]
To uninstall
Code:
wget [url]
For the Apf and Generic Iptables version:
To install
Code:
wget [url]
To uninstall
Code:
wget [url]
uninstall.synd ; ./uninstall.synd
I didnt get to try the apf version out much but have used the csf version all day with no issues
Note to makers of dos-deflate: Im not too keen on all this licensing stuff or what I am supposed to do when I modify someone else script so let me know what I need to do to keep from making anyone mad.
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Apr 24, 2008
server notice : kernel: possible SYN flooding on port 110. Sending cookies. and down.
how to disable flood on port 110, flood port 443!
EX : disable telnet on port : 21,445,110,53
how to disable telnet on port 21,445,110, with cmd (telnet ip(host) port)
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Mar 15, 2007
I am noticing some packet loss on one of my boxes, most notably when i'm accessing the webmail (however i'm pretty sure it's not that)
Can anyone offer some tips as to how to nail this down?
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Dec 23, 2007
I have a dedicated windows 2003 server at a colocation facility that i use for game server hosting. Over the past 7 months, packet loss has become horrible with random periods of massive lag. My host says it's something on my end. I use a firewall with SPI enabled. Could that be causing it?
Strange thing is, the first few months my server was at that colo, they only had around 40 other servers on a single OC-192 pipe and i never had packet loss despite having the same SPI firewall. But now they have over 300 servers on the same OC-192 pipe. Could the packet loss be caused by my SPI firewall or them overloading the network with servers?
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Jun 17, 2009
We have a license application client(IBM/LUM) that connects to a license server outside our network.
The clients works this way... it binds a random port and tries to connect to the remote IP with UDP port 1515.
Through wireshark I could see that it reaches the destionation, although the way back is unreachable.
If I add this random port to our router Port Forward rule, it works perfectly. Although this is not a solution cause the port is changing every time.
Isnt this strange? Other applications open random ports as well and comunication is two-way reachable.
If I connect directly to the internet, it works perfectly as well.
What can I try to do with our ZyWall USG300 Router to fix this situation?
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Jun 10, 2009
Basically I registered with a new host. They sent me the details with obviously includes the IP address. I tested the IP address on just-ping.com and it came back with all of them having between 80% to 100% packet loss. Surely this is not normal is it? I havent moved my domain yet but it doesnt look good does it? Should I cancel?
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Mar 2, 2008
I restored a database and got this error:
ERROR 1153 (08S01) at line 2663: Got a packet bigger than
'max_allowed_packet' bytes
why I got this error and how to fix this? vbulletin staff told me that I have to increase the 'max_allowed_packet' in my.cnf, then restart MySQL. Where can I find this file? I use Directadmin control panel for my dedicate server.
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Jul 11, 2008
Anyone else experiencing packet loss with a GoDaddy VDS?
I'm in the 208.109.93 subnet.
--- google.com ping statistics ---
200 packets transmitted, 53 received, 73% packet loss, time 199086ms
rtt min/avg/max/mdev = 41.970/42.813/46.022/0.994 ms
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Dec 11, 2007
with two 3com 3870 switches.
Our setup looks like this
Computer A (GigE) Switch 1 (gigE) Media Converter (Fiber Run) Media Converter (gigE) Switch 2 (gigE) Computer B
We have a cross connect in our data center that uses media converters (fiber) to regular 1000FD on each end.
Each end of the 1000FD handoff is plugged into port 1 of the 3870's (switch 1 and switch 2).
Pinging from Computer A to Computer B we receive a 50% packet loss.
Pinging from Computer B to Switch 1, no packet loss.
Pinging from Computer A to Switch 2, 50% packet loss.
Looking in the interface, the port 1's on each switch auto negotiate to 1000FD, however flow control shows as off.
We asked our data center to run tests on the media converts and fiber runs and everything comes back 100% fine. Has anyone seen a weird issue like this before with 3com switches not playing nicely with media converters?
I have no clue whats going on and our data center said the fiber run/media converter is fine... [url]
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Apr 12, 2007
I having having issue with few of my servers sending Reset packet to a particular IP. I have disabled my firewall and noticed that few machines (Unix/Windows) is still sending Reset package to one IP only. Reset packet will be sent over on all ports except icmp ping.
Anybody know where to check? Or the server on the other IP is having problem which cause my servers to send the Reset packet
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Jul 9, 2007
I have smokeping monitoring my game servers and so far in the little time that it has been running all my game servers have been encountering an average of 4 to 10% packet loss. Are there are tweaks i can run on the server computer to reduce packet loss? (registry modifications, etc.)
I downloaded a TCP tweak program called "TCP Optimizer" is it safe to run on a Windows 2003 Server OS?
The colo connection is an OC 192 and i have a 100Mbit ethernet card.
Here are my current TCP settings:
Quote:
[SYSTEMCurrentControlSetServicesTcpipParameters]
TcpWindowSize=-1
GlobalMaxTcpWindowSize=-1
EnablePMTUDiscovery=-1
EnablePMTUBHDetect=-1
SackOpts=-1
DefaultTTL=-1
TcpMaxDupAcks=-1
Tcp1323Opts=-1
DisableUserTOSSetting=-1
DefaultTOSValue=-1
[SYSTEMCurrentControlSetServicesAfdParameters]
DefaultReceiveWindow=-1
[SoftwareMicrosoftWindowsCurrentVersionInternet Settings]
MaxConnectionsPerServer=-1
MaxConnectionsPer1_0Server=-1
[SYSTEMCurrentControlSetServicesICSharingSettingsGeneral]
InternetMTU=-1
[SOFTWAREMicrosoftWindowsCurrentVersionExplorerRemoteComputerNameSpace{D6277990-4C6A-11CF-8D87-00AA0060F5BF}]
{D6277990-4C6A-11CF-8D87-00AA0060F5BF}=-1
[SYSTEMCurrentControlSetServicesDnscacheParameters]
MaxNegativeCacheTtl=-1
NegativeCacheTime=-1
NetFailureCacheTime=-1
NegativeSOACacheTime=-1
[SOFTWAREPoliciesMicrosoftWindowsPsched]
NonBestEffortLimit=-5
[SYSTEMCurrentControlSetServicesTcpipServiceProvider]
LocalPriority=499
HostsPriority=500
DnsPriority=2000
NetbtPriority=2001
[SystemCurrentControlSetServicesLanmanServerParameters]
SizReqBuf=-1
[SYSTEMCurrentControlSetServicesNdisWanParametersProtocols]
ProtocolMTU=-2
[SYSTEMCurrentControlSetServicesTcpipParametersInterfaces{D63AC0FA-D2C9-4D83-B057-31A353516AB3}]
MTU=-1
TcpWindowSize=-1
[SYSTEMCurrentControlSetServicesPschedParametersAdapters{D63AC0FA-D2C9-4D83-B057-31A353516AB3}]
NonBestEffortLimit=-2
[SYSTEMCurrentControlSetServicesTcpipParametersInterfaces{8190D94A-3B2D-45C4-998D-312E99D6061D}]
MTU=-1
TcpWindowSize=-1
[SYSTEMCurrentControlSetServicesPschedParametersAdapters{8190D94A-3B2D-45C4-998D-312E99D6061D}]
NonBestEffortLimit=-2
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Apr 25, 2007
How to check in Unix machine? My server is sending a Reset packet to the specific IP.
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May 17, 2009
I have a home CentOS server and here is my issue
When I try to connect to it via SSH its laggy and often times out. I also notice packet loss.
My home network is 100 Mbps and the router is a crappy netgear WPN824 V3
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Jan 11, 2008
How do packet losses affect running of a website, say i get packet loss for some site like around 30-40% but can still browse their websites, so how do packet losses affect working of a website ?
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Nov 3, 2007
Recently I have been having this problem with two high traffic servers on two different network.
Both servers are Quad-Core Xeons with CentOS 4.5 x86_64 and they are on 100mbps full duplex network. Software configuration is Nginx+Apache+MYSQL control panel is Directadmin.
The servers are serving lots static files and some php scripts.
When the servers start push near or over 30mbps, there will be packet loss when I ping them. around 5% loss, push more bandwidth the more packet loss. I have checked all the log files, I don't see any unusual errors.
Server Load is fine. The NICs were on 100mbps full-duplex mode.
The datacenters claim the networks were fine and all the other servers running on the same switches were fine with no packet loss.
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Mar 19, 2007
I'm trying to find out why a single interface is causing packet loss on my entire network.
The network consists of four 2924's trunked to a 3550. I have about 20 vlans and a single default route for all traffic my uplink.
The network is perfect until I enable a single server. After I issue a 'no shut' on the interface packet loss is anywhere from 5% to 20% for anything going through the 3550 or even pings from the 3550 to other switches or the uplink.
Here's the statistics/settings of the interface after 1 minute of activity:
Code:
interface FastEthernet0/1
description 228
switchport access vlan 58
switchport mode dynamic desirable
speed 100
duplex full
spanning-tree portfast
FastEthernet0/1 is up, line protocol is up (connected)
Hardware is Fast Ethernet, address is 0014.f2e6.df01 (bia 0014.f2e6.df01)
Description: 228
MTU 1500 bytes, BW 100000 Kbit, DLY 100 usec,
reliability 255/255, txload 1/255, rxload 6/255
Encapsulation ARPA, loopback not set
Keepalive set (10 sec)
Full-duplex, 100Mb/s, media type is 10/100BaseTX
input flow-control is off, output flow-control is unsupported
ARP type: ARPA, ARP Timeout 04:00:00
Last input never, output 00:00:00, output hang never
Last clearing of "show interface" counters 00:01:01
Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 0
Queueing strategy: fifo
Output queue: 0/40 (size/max)
5 minute input rate 2536000 bits/sec, 924 packets/sec
5 minute output rate 341000 bits/sec, 469 packets/sec
60922 packets input, 21630544 bytes, 0 no buffer
Received 0 broadcasts (0 multicasts)
0 runts, 0 giants, 0 throttles
0 input errors, 0 CRC, 0 frame, 0 overrun, 2 ignored
0 watchdog, 0 multicast, 0 pause input
0 input packets with dribble condition detected
31585 packets output, 2859788 bytes, 0 underruns
0 output errors, 0 collisions, 0 interface resets
0 babbles, 0 late collision, 0 deferred
0 lost carrier, 0 no carrier, 0 PAUSE output
0 output buffer failures, 0 output buffers swapped out
Transmit FastEthernet0/1 Receive
3583183 Bytes 27018085 Bytes
39516 Unicast frames 76403 Unicast frames
46 Multicast frames 0 Multicast frames
0 Broadcast frames 0 Broadcast frames
0 Discarded frames 0 No dest, unicast
0 Too old frames 0 No dest, multicast
0 Deferred frames 0 No dest, broadcast
0 1 collision frames
0 2 collision frames 0 FCS errors
0 3 collision frames 0 Oversize frames
0 4 collision frames 0 Undersize frames
0 5 collision frames 0 Collision fragments
0 6 collision frames
0 7 collision frames 4355 Minimum size frames
0 8 collision frames 56237 65 to 127 byte frames
0 9 collision frames 1205 128 to 255 byte frames
0 10 collision frames 14 256 to 511 byte frames
0 11 collision frames 67 512 to 1023 byte frames
0 12 collision frames 14528 1024 to 1518 byte frames
0 13 collision frames
0 14 collision frames 0 Flooded frames
0 15 collision frames 3 Overrun frames
0 Excessive collisions 0 VLAN filtered frames
0 Late collisions 0 Source routed frames
0 Good (1 coll) frames 0 Valid oversize frames
0 Good(>1 coll) frames 0 Pause frames
0 Pause frames 0 Symbol error frames
0 VLAN discard frames 0 Invalid frames, too large
0 Excess defer frames 0 Valid frames, too large
0 Too large frames 0 Invalid frames, too small
3672 64 byte frames 0 Valid frames, too small
34066 127 byte frames
2152 255 byte frames
110 511 byte frames
38 1023 byte frames
28 1518 byte frames
CPU utilization for five seconds: 13%/3%; one minute: 12%; five minutes: 9%
77 1317620 3220725 409 9.27% 8.35% 6.20% 0 IP Input
How does 1400 packets/second (4mbits) cause my 3550 to drop packets?
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May 13, 2008
Our network have been ddosed very heavily for the last 15 days.
These attacks are relatively small 50 - 100 mbits at most but in very very high PPS rate.My firewall counts 10Billion packets in a single hour of an attack period.
We are dealing with these attacks with a combination of freebsd pf transparent bridge firewalls and mostly null routing.
I were able to capture some packets from different attacks from last week and today.
After deeply checking these attack capture files I can see that our attack comes from several thousands different spoofed Ip addresses but always the same mac address in their packet headers.So I thought if this attack is coming to us from a single machine rather than hundreds of different zombie servers.
I don't have a clue how to trace back this attack and find the real ip address behind. My upstream provider also don't have enough knowledge to help me.
So after todays attack I thought about sharing my capture files during attack and hope that someone here will help me. And show me a way to trace back these attacks.
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Mar 20, 2008
ip_conntrack: table full, dropping packet
What does that error mean? It's related to iptables right? When I do this cat /proc/sys/net/ipv4/ip_conntrack_max, I get
65536
I increased it
131072
Because someone recommended me this number because I have 4gb of RAM. But I still get the table full errors or
host kernel: printk: 500 messages suppressed
What should I do? Should I keep increasing the number? How do I know how much I can increase it by?
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Jul 6, 2008
a tool that can measure how much packet loss we are having on a given server by looking at the packets being sent from it. I.e, something than looks at all TCP/80 connections and measures how many packets and bytes are being retransmitted vs actual packets and bytes sent.
This documents explains it:
[url]
We need this to measure network performance of different hosts where we have dedicated servers. This would be a good way of measuring performance with the actual data of our users.
Does anyone know of such tool? I.e, something that can say
2532 packets/second - 132 retransmits/second (4.8%)
25.43Mbps/sec total traffic - 24.84 Mbps/sec actual data sent - 0.59Mbps retransmits
Even better if it can then break it out on IP prefixes. like
192.0/16: 0.2% retransmits
192.1/16: 3.2% retransmits
192.2.16: 0.3% retransmits
192.3/16: 22.5% retransmits
192.4/16: 0.3% retransmits
This would be a good indicator of connectivity between the host where the tests are ran and other specific hosts.
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Mar 30, 2007
I have 2 identical boxes with FC6 and the same settings and almost the same amount of traffic.
Kernel is 2.6.20-1.2925.fc6 SMP
One is running without problem. The other become slow after few days and from errors I get this message:
nf_conntrack: table full, dropping packet
The table do not clean up automatically as reboot solve the problem. How to flush nt_conntrack table without reboot?
The limit is 65536, setting it double seems to solve the problem but I'm not sure it is the way to go.
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Aug 1, 2009
I am facing high ping and packet loss issues with a server hosted at hetzner.de (CentOS + WHM)
For some unknown reason pings go high and stay like this (average 1500ms) until I reboot the server.
Here is a screenshot of tracert from server to me: [url]
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Mar 8, 2008
I recently switched over to SoftLayer for dedicated hosting and the servers are great. However we've been getting hit on and off with massive (50-80%) packet loss, which has been crippling our performance and causing all sorts of problems
I put in a support ticket and they linked me to the Internet Health Report website and said it was due to one of their bandwidth providers (I think Global CrossinG) and not on their internal network and to be patient as it could take time to resolve
Are any other SoftLayer customers going through this? Is this an unusual occurrence? I feel like if it was really one of their partners that it would be affecting a lot of their customers and it would be a high priority issue right?
I'm kind of stuck on what to do; I just invested a lot of energy into moving content onto these new servers and am concerned about whether to wait it out or whether to start finding a new company. This kind of packet loss is really unacceptable...
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Jun 10, 2008
root@server [~]# tail -f /var/log/messages
Jun 10 14:14:49 server kernel: printk: 56 messages suppressed.
Jun 10 14:14:49 server kernel: ip_conntrack: table full, dropping packet.
Jun 10 14:14:54 server kernel: printk: 59 messages suppressed.
Jun 10 14:14:54 server kernel: ip_conntrack: table full, dropping packet.
Jun 10 14:14:59 server kernel: printk: 85 messages suppressed.
Jun 10 14:14:59 server kernel: ip_conntrack: table full, dropping packet.
Jun 10 14:15:04 server kernel: printk: 90 messages suppressed.
Jun 10 14:15:04 server kernel: ip_conntrack: table full, dropping packet.
Jun 10 14:15:09 server kernel: printk: 58 messages suppressed.
Jun 10 14:15:09 server kernel: ip_conntrack: table full, dropping packet.
Jun 10 14:15:14 server kernel: printk: 70 messages suppressed.
Jun 10 14:15:14 server kernel: ip_conntrack: table full, dropping packet.
Jun 10 14:15:19 server kernel: printk: 193 messages suppressed.
Jun 10 14:15:19 server kernel: ip_conntrack: table full, dropping packet.
Anyone know what this is about?
Using Centos / Cpanel
Linux server.domain.com 2.6.9-67.0.15.ELsmp #1 SMP Thu May 8 10:52:19 EDT 2008 i686 i686 i386 GNU/Linux
root@server [~]# sysctl net.ipv4.netfilter.ip_conntrack_max
net.ipv4.netfilter.ip_conntrack_max = 65536
I ran this in the meantime.
sysctl -w net.ipv4.netfilter.ip_conntrack_max=72000
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