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166

Ports are a concept of UDP and TCP. Ping messages are technically referred to as ICMP Echo Request and ICMP Echo Reply which are part of ICMP. ICMP, TCP, and UDP are "siblings"; they are not based on each other, but are three separate protocols that run on top of IP. Therefore you can not ping a port. What you can do, is use a port scanner like nmap. nmap ...


123

See below for an example of a scam that was sent to me, pretending to be from my friend, claiming she has been robbed and asking me for financial aid. I have changed the names — I am "Bill," and the scammer has sent an email to bill@domain.com, pretending to be alice@yahoo.com. Note that Bill forwards his email to bill@gmail.com. First, in Gmail, click show ...


115

Similar to mpez0's answer, but I like a good car analogy... I'm choosing the UK for this, since that's where I live. Imagine you live in a world where people follow road signs without question, and you happen to live right up in the north of Scotland, about as far from London as you can without crossing water. You live in a small town, and one day you ...


114

When retracting a RJ45 plug through narrow tubing or around corners, the clip tends to snap off, effectively making the network cable useless in most environments. The rubber dome (most commonly referred to as a cable boot) nearly always prevents that from happening. You wouldn't know how many network cables I've seen with broken off clips.


112

From experience, those retention clips break off a lot on the first sort of cables - those are fine for cables that are well protected and/or going to be plugged in and forgotten, but the moment those clips bend the wrong way, they break, and you end up with a cable that dosen't clip in place. They also snag each other sometimes and are just a PITA. Cable ...


106

There is nothing preventing you from attaching a box configured with someone else's IP address to the internet. However, this won't necessarily cause any issues for anyone else but yourself. If you steal someone else's IP address outside of the subnet that you are physically connected to, the only thing you will accomplish is not being able to receive any ...


94

What are MAC addresses used for? MAC addresses are the low level basics that make your ethernet based network work. Network cards each have a unique MAC address. Packets that are sent on the ethernet are always coming from a MAC address and sent to a MAC address. If a network adapter is receiving a packet, it is comparing the packet's destination MAC ...


89

If you don't want to replace the cable or install a new jack, you have a few of options: Glue it into a coupler or a short extension like one of the following (with the coupler you will need another short run of cable on the other side): Repair it with a zip tie. Use this guide for instructions: ...


66

This is because ping on Windows Vista and newer Windows uses IPv6 by default when available. ::1 is a shortened notation of IPv6 loopback address - equivalent of IPv4 loopback 127.0.0.1. The full notation of the abbreviated ::1 IPv6 address is 0000:0000:0000:0000:0000:0000:0000:0001. If you want to force ping to use IPv4 instead you can specify the IPv4 ...


63

There's specifically a blackhole prefix in IPV6, as described in RFC 6666, it's 100::/64. IP4 does not have an explicit black hole like that, but a non-existent host on one of the reserved blocks would have that effect. (e.g., 240.0.0.0/4 is "reserved for future use" and will not be routed by anything.)


50

Short answer : you can't prevent them from sniffing your traffic, but you can make it meaningless for them by using encryption. Either use encrypted protocols (HTTPS, SSH, SMTP/TLS, POP/TLS, etc.) or use encrypted tunnels to encapsulate your unencrypted protocols. For example, if you use HTTPS instead of HTTP, the content of the webpages you fetch will ...


44

The MAC-Address (Media Access Control address) in general is the identifier of devices in a network. So every NIC (network interface controller found in a router, PC, network-printer, server etc.) have MAC addresses. Some servers have more than one network card built in and therefore have multiple MAC addresses. The MAC address is 6 Bytes long (6 octets). ...


44

In 10BASE-T and 100BASE-TX, one pair of wires is used for transmitting, and one for receiving. That is, one pair is the pair the Ethernet host transmits on, and the hub or switch receives on, and the other pair is the pair that the the hub/switch transmits on, and the Ethernet host receives on. If you split the cable with a simple passive splitter, you're ...


43

I use Telnet, since its built into lots of platforms with no additional downloads. Just use the telnet command to connect to the port you want to test. If you get the message below, or a message from the service itself, then the port is alive. Minty16 ~ $ telnet localhost 139 Trying 127.0.0.1... Connected to localhost. Escape character is '^]'. If you ...


39

Try to ping 8.8.8.8, it's Google primary DNS server. I always ping it to verify my connection and I never found it down. Alternatively you can try 8.8.4.4, which is Google secondary DNS.


37

TL;DR> MAC addresses are a low level component of an Ethernet network (and some other similar standards, such as WiFi). They allow a device to communicate with a machine on the local physical network (LAN), and cannot be routed across the Internet - because physical hardware might in theory be plugged in anywhere in the world. By contrast, IP ...


35

Cable modems aren't like your home router (ie. they don't have a web interface with simple point-and-click buttons that any kid can "hack" into). Cable modems are "looked up" and located by their MAC address by the ISP, and are typically accessed by technicians using proprietary software that only they have access to, that only runs on their servers, and ...


32

There is such a thing as network Black hole. If there are no devices in the network with IP address 192.168.0.10, then this IP address is kind of black hole and it will "discard" all the traffic to it, simply because it does not exist. Protocols which keep track of connection state (TCP) can detect a missing destination host. It will not happen with UDP ...


31

Make a bash script which adds restrictive iptables rule. Put this script in monthly cron. Inside the bash script make a condition - if file ~/do_not_block_friends exists and its modification time is within of month period (stat -c %y filename) - do not run the script. Once they pay you do touch ~/do_not_block_friends. Script will run and see that ...


31

There's a standard protocol for that, called the Spanning Tree Protocol. As the name suggests, it works by building a spanning tree of the network — a subset of the network that includes all nodes but contains no loops — and then disabling any ports that aren't part of the spanning tree. If a link in the spanning tree fails, e.g. if someone unplugs a ...


30

In short, the answer is No First of all, as you have correctly stated you cannot exceed the speed limit set by your ISP. This just won't happen. It is a hardware restriction of the connection you are using, whatever that connection is - fiber, ADSL, DialUp, 3g, 4g, ... A software that claims to overcome the restriction described above is clearly ...


29

Can you (temporarily) enable MAC filtering on the Wifi? With that, you should be able to whitelist one MAC at a time and see which one is the culprit. For what it's worth, I would suspect someone is running BitTorrent or something similar.


28

No. Analog telephone modems (a.k.a. POTS - "Plain Old Telephone Service" modems) worked because when the traditional telephone network (a.k.a the PSTN - "Public Switched Telephone Network") digitized the audio, it did so with 8-bit samples 8,000 times per second, for a total of 8 bits * 8 kHz = 64,000 bps digital audio. It wasn't possible to fully utilize ...


27

You could be behind a carrier-grade NAT (CGN) with an "IP address pooling" behavior of "Arbitrary", rather than the recommended behavior of "Paired". See http://tools.ietf.org/html/rfc4787#section-4.1 . Or you could be behind a transparent HTTP proxy that causes similar problems, but only for HTTP.


26

That's an anti-snag boot meant to protect the clip when pulling the cable through other cabling, conduit, and other tight spaces. You can carefully clip it off if you don't care about the anti-snag capability. There are some other anti-snag styles that can work better in tight locations: I've found that first style works well in our 48 port ethernet ...


23

Most modern ISPs (last 13 years or so) will not accept traffic from a customer connection unless it has a source IP address that they would route to that customer were it the destination IP address. This is called "reverse path forwarding". See BCP 38. ISPs either do not use dynamic routing protocols with their customer connections or filter the routes they ...


23

They are used for packet transfer: on an Ethernet network, there are a number of devices, and the MAC address specifies which device should receive the packet. Ethernet switches will use it to choose which port to send out a received packet on.


21

You cannot just force a program to use UDP instead of TCP, without rewriting parts of the program itself. These protocols are just too different to be interchangeable. TCP is stream-oriented (the receiver sees everything as a continuous stream in the exact order that the sender output it); UDP is datagram-oriented (each datagram is sent in a separate ...


20

Even when (some of the) other answers are more practical to find your problem, as long as the original question request something like "How to find and ARP poisoning running?", I am going to give an easy-to-apply in a few steps method to detect ARP Poisoning valid for any Windows version extracted from a generic (non-WiFi), faster and simpler method here.: ...


20

Consider the analogy of your house address. One day you decide to change your address from "123 First Street" to "1600 Pennsylvania Avenue". What difference does it make outside your own property lines? None - because the rest of the world still behaves as if the physical location of your house didn't change, the name of your street didn't change, the city ...



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