Questions tagged [packet]

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23 views

What's the expected behavior in TCP when hosts don't specify the MSS during handshake?

Let's suppose there are two hosts A and B and they are going to communicate over TCP. I am curious about the behavior of TCP related to MSS. Wikipedia says default value of MSS is 536. But, RFC-793 ...
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1answer
20 views

Is it possible to capture packets of router which i connected through wifi of my laptop

I want to capture all traffic of router I can only connect with wifi no physical access and I do have access to configuration page of router
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15 views

Does tcpdump guarantee packet integrity?

In normal use of tcpdump without any parameter, does it guarantee? tcpdump -i eth0 -w file.pcap In using tcpdump rotating by time with -G parameter, does it guarantee? tcpdump -i eth0 -w file.pcap -...
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1answer
692 views

Is there is any tool/way to find out why packet is getting dropped due to an arp cache full?

My developer hypothesis is packet is getting dropped at arp layer. We increased the default value of neigh.default.gc_thresh3 1024 --> 2048 and now everything looks good. But I want to understand is ...
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1answer
85 views

Performing tasks and custom logic on network packets

I'm looking for a way to process packets in a Linux server in a particular fashion - I need to run some custom logic on every packet, then (possibly) take some actions on the packets and let the ...
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21 views

Use 2 dns for packet destinations in openvpn

I have a vps and openvpn is already installed on it. Clients' packet is important for me, if our packet destinations' IP is from Iran, using openvpn is not required but when the IPs are from out of ...
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34 views

HTML code trying to load PDF file from Site using ssl with self signed certificate

My employer has a web application that loads a pdf file onto the client browser by having a code that does the ff: embed src="https://somepage.somesite.com/folderpath/somefile.pdf" width="100%" ...
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1answer
59 views

Can a router be connected to a both a subnet and a subnet inside that subnet?

Can a router be connected to both a subnet 1 and a subnet 1.1 which is a subnet inside of subnet 1? For example, can a router be connected and sent packets to subnet 223.1.17.128/25 and 223.1.17.192/...
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1answer
81 views

IPTables or alternate solution to block the first attempt to connect then allow further attempts from same IP

I have a unique situation in which a DDOS attack for a certain game is sending realistic player connection packets that seem to perfectly mimic a real player's connection packet. These typically ...
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1answer
52 views

In iptables, if a packet is ACCEPTed in one table, does it bypass the next table?

If a packet is ACCEPTed from, say, the INPUT chain of the mangle table, will it bypass the INPUT chain of the filter table and go straight to the local process? Or will the INPUT chain of the filter ...
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48 views

FreeBSD: redirect some UDP traffic from one port to another

I have some specialized DNS servers running on FreeBSD 11. A few people keep hammering on them and I would like to give them different answers. So I'd like to divert UDP traffic from those hosts from ...
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1answer
92 views

Force jumbo packet fragmentation

We are in a cluster environment. We have compute nodes with jumbo packets enabled and a MTU of 9000. We are running into some issues in tracebacks to an address outside of our lan, where jumbo packets ...
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1answer
55 views

How packet is transmitted over the network? [closed]

I am writing discrete event-driven simulator to measure time between sending datasets over network. If multiple processes sends n packets through network they (packets) will go one after one through ...
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2answers
443 views

Openvpn fails behind firewall but another VPN Works

Well I have spent last 48 hours trying to debug this but I'm about to give up now. Mobile carrier in our country has a daily social bundle in which we can use ONLY whatsapp, facebook and snapchat &...
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1answer
373 views

How to send outgoing TCP packets on Windows through a remote Linux server?

Let's say I have a Windows computer and a Linux server. I'm looking for a way to route outgoing TCP packets on the Windows computer (all ports) through the Linux server. The Linux server would have ...
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1answer
2k views

Understanding SoftEther VPN packet log

Help me to identify each part of a packet log from softether VPN. for example, the below given is a packet log. 2017-06-07,23:40:20.888,SID-USER-[L2TP]-15,SID-SECURENAT-1,CA9DC6D826F0,00AC3A3F04D0,...
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2answers
1k views

How to mark packets depending on hostname?

We can mark packets on the basis of IP addresses in the following way - iptables -A FORWARD -t mangle -s 123.2.3.4 -j MARK --set-mark 1 How to mark packets depending on the hostname? I tried this - ...
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1answer
61 views

High Traffic from Content Delivery Networks

I am having trouble on our school network recently. When browsing the internet users will often get an error from the browser saying "No Internet DNS_PROBE_FINISHED_NXDOMAIN" but when they refresh the ...
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1answer
4k views

Transportation Layer vs Network Layer [closed]

I am a networking student, and I am learning about the OSI system for networks. The concepts for this system are all pretty complicated, but the main issue that I'm having is the main differences ...
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462 views

Route HTTP packets into tun/tap interface

What I simply want is to redirect all HTTP packet from any interface to my tun/tap interface. A scapy script will listen on this interface and do some treatments to these packets. First, I created a ...
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1answer
1k views

Accept ICMP packets (ping) with specific length - Iptable rules

I am going to filter Ping request to my server, and only accepts ping request with length 920. ping -l 920 serrveraddress I am using the following two command in iptables iptables -A INPUT -p icmp -...
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1answer
103 views

Linux firewall packet handling

When a client communicates with a the server via HTTP, for example, there are many packets going in both directions. It means from the client to the server and vice versa. I would like to ask how ...
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1answer
105 views

Drop packet containing the selected string

How can I drop all packets on windows server that are containing a specific string? The string is: TSource Windows Firewall doesn't seem to have this kind of option.
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1answer
234 views

Force Windows to send packets as soon as they arrive the nic

I have a network application running on Windows Server 2008 R2, that must send small packets in a very short time interval, each microsecond matters. My problem is that windows accumulates the packets ...
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1answer
11k views

Outbound Packets Dropping / Timeouts - Only with Azure

I have an issue with packets dropping to a third party data center in Florida, USA. The issue only occurs on Azure Virtual Machines, no matter which data center the VM is in. I've done the same tests ...
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1answer
653 views

Extremely flaky connection to our EC2 instance through one connection, but not others

We have a robotic coffee barista deployed at the Dell campus in North Austin, with internet service through Time Warner Cable. We have been fighting intermittent connection losses between 10PM - 1AM ...
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1k views

Getting chunks of high ms when pinging local / external IP addresses?

I am having difficulty identifying what a specific problem with one of your vlaned networks. They have a voip phone which regularly cuts out during long phone calls. I have done several ping tests ...
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1answer
2k views

iptables rules for blocking specific packets [closed]

Im using the following iptables rule: iptables -A INPUT -p tcp -m tcp --tcp-flags PSH,ACK PSH,ACK -m length --length 52 -m state --state ESTABLISHED -j DROP It does it's job for blocking the ...
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1answer
2k views

iptables connlimit: exclude multiple IP addresses

I have currently this IPTABLES command: iptables -A INPUT -s ! 192.168.0.2 -p tcp --syn -m connlimit [...] -j DROP As far as I know, such rule limit some number of connections following various ...
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0answers
67 views

Split TCP packet - Data layer vs IPv4Layer

What is the different between split TCP packet in the Data layer compare to split the packet in IPv4Layer ?
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2answers
929 views

How to redirect a packet with iptables that match a certain pattern? (eg a QUERY command with UDP)

I have a certain packet that I want at all times to be redirected to a specific ip on my virtual network interface. As for now my iptables is setup like this: (the commands, I use \ as for now to ...
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1answer
264 views

How many times does switch calculates FCS?

Does a switch calculate the Frame check sequence (FCS) before sending packets? Because packet shouldn't change, so FCS should also stay the same.
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1answer
96 views

How many data packets does it take to log in to facebook? [closed]

I want to find out how many packets are sent when visiting a site on the web. What's a good program that would help me get this kind of data?
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1answer
33 views

See historical packet receipt statistics in Windows

I know this is a long shot, but it would be really useful to me right now. Does anyone know of a Windows function or 3rd party tool that can show stats about the receipt of packets on a network ...
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4answers
250 views

Is there anyway to tell what user will receive data from inbound packet?

In linux, considering this use case: 1. User initiates http request for webpage to remote server 2. Remote server answers request and sends packets Is there any reference to the user who started ...
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1answer
3k views

Set udp packet size limit

I have a CentOS server with a JAVA application that receive UDP data packets, it works all OK until the packet is bigger than 584 bytes, I read something about and seems to be a limit of UDP protocol. ...
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1answer
989 views

tcpdump show strange packet with incorrect src ip and dst ip

I have private LAN with > 100 servers, in which, I have 3 server: x.x.x.37: run memcache on port 11211 (called s37 for short) x.x.x.241: run an application server, which connect to memcache on x.x.x....
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1answer
3k views

PF: Block all, but one subnet firewall rule?

I'm trying to do something that I thought would be relatively simple: Block all the traffic to a test server, other than my company's subnet. I've tried things along these lines (111.111.0.0 is my ...
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1answer
6k views

TCP Sequence & Acknowledgment numbers

I have looked through other questions on here involving the relevant topics, but I am still not clear on this. I have just been reading this explanation of TCP sequence & acknowledgment numbers. ...
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3answers
419 views

Is TCP header the same as TCP segment?

So, is a TCP header actually the same thing as a TCP segment? I was reading this page, where it reads near the end that: Even though it might seem they are, in most cases, when referring to the ...
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1answer
349 views

Viewing the packet-size of an incoming IP

I have been looking for a sulution to this for a few hours. after no avail im asking for help here. I need to watch my incoming packets by Size. in a format similar to: IP SIZE I have tried TCPDUMP ...
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3answers
3k views

How many packets will it take to send particular data?

If I know the maximum packet size is 1500 bytes say for Ethernet frame v2 then for example I want to transfer 1 KB over the Internet which is roughly 1024 bytes. Will the packet be split into many ...
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1answer
142 views

Understanding ARP traces during OS load

Consider the following ARP packets captured while a unix machine was booting. From the packets I understand that this machine whose MAC address is 00:22:22:22:22:22 is requesting information about ...
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2answers
251 views

Server sending packets every 5 minutes to 3 IPs

Been noticing in our firewall logs that three connections are being constantly established every 5 minutes from our web server and trying to send a packet to destination port 43 (whois port) cycling ...
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1answer
3k views

UDP maximum segment size

Environment: I am writing a UDP client-server application. the path MTU between client and server is 1500 bytes (with only a wireless link between them, so this value is pretty much stable). My system ...
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1answer
20k views

Why is the “don't fragment” flag set in https and ssh protocols?

I've found a lot of information specifying that this is the case, however, I am really looking for the reason behind this. Why is it necessary? Is it necessary?
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1answer
47 views

forwarding of small and large packets: any difference?

When it comes to simple forwarding of packets (no errors being generated), are packets processed faster by routers when they are small as opposed to when they contain a large payload? Or do routers ...
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0answers
368 views

Redhat 6.4 configured to log Martian packets but is not logging ll header

I am trying to investigate the source of martian packets I have been seeing on several servers connected to the same subnet. The logging of martian packets has been enabled in /etc/sysctl.conf. ...
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3answers
78k views

Excessive 'TCP Dup ACK' & 'TCP Fast Retransmission' causing issues on network. What's causing this?

I'm getting excessive TCP Dup ACK and TCP Fast Retransmission on our network when I transfer files over the MetroEthernet link. The two sites are connected by one sonicwall router, so the sites are ...
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1answer
135 views

How do routers manage multiple data streams? [closed]

Routers manage data connections between the internet and computers or connections between computers on a LAN. It makes sense that when, for example, a computer requests music from Pandora, that ...