33 votes
Accepted

Why are IP addresses given to each interface and not device? What would the implications of that be?

Connecting an interface to a network makes it a part of that network. Therefore, the IP address is a property of the connection, not the host. Likewise, a host can have many network connections and ...
Zac67's user avatar
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33 votes
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What stops someone from configuring their network with IP addresses they do not own?

Most likely if they're a big university they are their own ISP, using BGP to connect their network to the internet via a number of upstream networks. Nothing stops them from using IP addresses they ...
Teun Vink's user avatar
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31 votes
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Is multicast on the public internet possible? And if yes: How?

You cannot multicast on the public Internet, but you can multicast across the public Internet to another site by using a tunnel that supports multicast. Multicast routing is very different from ...
Ron Maupin's user avatar
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25 votes
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Is it common for ISPs to connect to each other directly?

Yes, this does happen quite a lot, and it is called private peering. It has some benefits over peering over an IXP: dedicated bandwidth, you can be sure you can use the full capacity of the ...
Teun Vink's user avatar
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21 votes
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Is it possible to specify a route for a packet to take?

It's theoretically possible, but not really in a practical sense. The IP protocol includes two options: Loose Source and Record Route (LSRR) Strict Source and Record Route (SSRS) They're both ...
Barmar's user avatar
  • 426
19 votes

Is multicast on the public internet possible? And if yes: How?

As an end-user, you cannot multicast across the Internet, unless using a tunnel. As a larger organization, like a video provider or an ISP, it is certainly possible to forward multicast packets ...
pHeoz's user avatar
  • 590
17 votes

Why are IP addresses given to each interface and not device? What would the implications of that be?

It would not be enough. Suppose I have a computer with three interfaces: eth0 (wired Ethernet), wlan0 (wifi), and vboxnet0 (virtualbox). One of the interfaces is connected to an internal network, one ...
Piskvor left the building's user avatar
14 votes
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How do routers on the backbone avoid IP address conflicts?

The RIRs assign addressing to the ISPs. An ISP not following the rules will quickly find itself ostracized and cut off from the rest of the Internet. IANA owns the addressing and assigns each of the ...
Ron Maupin's user avatar
  • 99.6k
12 votes

What are the differences in the contents of datagrams, frames, and network packets?

The terms Frame, Packet, and Segment exist to create abstractions from what one layer is responsible for verses the others. To explain that, and to answer your question thoroughly, I'm going to start ...
Eddie's user avatar
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12 votes

What stops someone from configuring their network with IP addresses they do not own?

What stops them from attributing their routers and hosts already in use IP addresses? Nothing. Over the years, I have seen both organizations of all sizes, both public and private, do this including ...
YLearn's user avatar
  • 27.3k
11 votes

Do Bluetooth Devices have MAC address with the same specification as the MAC addresses of the Ethernet and Wi-Fi Network cards?

Bluetooth devices are required to have a unique device address, assigned from the same registry as Ethernet and Wifi MAC addresses. Quoting the Bluetooth specification version 5.0 volume 1: Each ...
fgrieu's user avatar
  • 243
10 votes
Accepted

How are IPv4 Addresses provided uniquely to domains?

Who mainly provides IP addresses to domains? As in, who commands, "www.google.com, 103.233.38.93 is yours; www.stackexchange.com I will assign 104.16.115.182 to you; etc." Normally IP addresses are ...
Peter Green's user avatar
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10 votes
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Is it true that the fd00::/8 address range (ULA) in ipv6 is for machines that you NEVER want to speak with anything on the Internet?

IPv6 packets addressed in the IPv6 ULA address range, fc00::/7, can not be routed on the public Internet. Remember, though, that interfaces can have multiple IPv6 addresses, including Link-Local, ...
Ron Maupin's user avatar
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10 votes
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Analyze Network Traffic by Autonomous System Number?

You can certainly do this with Wireshark. In the menu choose Statistics > Endpoints and you will see a window like this: You might need to copy and paste into Excel to sum the bytes per AS, or use ...
jonathanjo's user avatar
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10 votes

Why are IP addresses given to each interface and not device? What would the implications of that be?

A device that has an IP address exists within a network. A Router is a device who's primary purpose is to pass traffic between networks. For a Router to pass packets between two networks, it must ...
Eddie's user avatar
  • 15k
9 votes
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Finding Subnet Ranges of IPv6

Basically, with IPv6, most subnets will just be /64. Using subnets of other sizes, with a couple of exceptions, will break features of IPv6. See RFC 5375, IPv6 Unicast Address Assignment ...
Ron Maupin's user avatar
  • 99.6k
9 votes
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What's the domain of an IP?

It is a routing domain. That is a block of addressing controlled by a single entity. For example, Company X could be assigned 10.11.0.0/23, Company Y could be assigned 10.11.2.0/23, and Company Z ...
Ron Maupin's user avatar
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9 votes
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Is QoS an issue for VOIP calls over the Internet? If not, why not?

VoIP over the public Internet can be a problem, but it usually works good enough, most of the time, although there can be times where it sucks. Most ISPs have extra cost features where they will honor ...
Ron Maupin's user avatar
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8 votes
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Private IP inside internet?

Traceroute deliberately sends packets with low time-to-live values to make the routers between you and your destination send back ICMP TTL exceeded messages. The traceroute output is basically the ...
Gerben's user avatar
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8 votes
Accepted

Why is the internet *not free?

Most ISPs have to buy service from other ISPs to be able to reach every part of the internet. That is called "transit". If you start a small ISP you usually buy transit from one or more bigger ISPs. ...
Sander Steffann's user avatar
8 votes
Accepted

When X.25 or ATM were used in ISP networks or Internet backbone was the protocol running over this layer still TCP/IP?

Think of it this way: we used the fastest links we could buy to run IP over the wide area between the nodes of the Internet. So that was 56/48Kbps X.25, and later 1.44/2Mbps Frame Relay, and later ...
vk5tu's user avatar
  • 1,171
8 votes
Accepted

Class A most significant bits '0' as in RFC1166 or older or '00' as suggested in RFC4632?

It appears to be a typo in that RFC. Notice that the header of the RFC says Errata Exist. It is not uncommon for things like that to happen. That particular error is corrected in the errata. See the ...
Ron Maupin's user avatar
  • 99.6k
8 votes

What are the differences in the contents of datagrams, frames, and network packets?

Note: the term datagram is used in various ways. If we stick to RFC1594 a datagram is A self-contained, independent entity of data carrying sufficient information to be routed from the source to the ...
JFL's user avatar
  • 19.7k
8 votes

Is QoS an issue for VOIP calls over the Internet? If not, why not?

I'm trying to decide whether I should buy SIP trunks from my ISP or a 3rd-party. and... Is QoS an issue for VOIP calls over the Internet? Short answer: End-to-end QoS is NOT offered on the public ...
Mike Pennington's user avatar
8 votes

What stops someone from configuring their network with IP addresses they do not own?

Nothing will stop them using the addresses on their own machines. What happens if they try to advertise them to the Internet depends on how sloppy their providers are. If their providers are ...
Peter Green's user avatar
  • 13.3k
8 votes

Is a point-to-point T1 line literally a line in real life?

No. There may be a dedicated circuit between the routers and the nearest telco central office, but between offices they are switched and multiplexed onto other, higher capacity circuits. Today, most ...
Ron Trunk's user avatar
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8 votes
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In practice, how are BGP Advertisement destinations determined and configured?

Some connection between the two ISPs is needed. Dedicated fibers (for example in a datacenter they're both present in) is very common. But there are other possibilities: a layer 2 connection (for ...
Teun Vink's user avatar
  • 17.4k
7 votes
Accepted

PPPoE interface doesn't use ARP

PPP doesn't use MAC addresses or ARP the way ethernet does, so no, there will not be ARP in PPP, but there may be ARP in the ethernet which carries the PPP frames. You will not see anything ethernet-...
Ron Maupin's user avatar
  • 99.6k
7 votes

Is it true that the fd00::/8 address range (ULA) in ipv6 is for machines that you NEVER want to speak with anything on the Internet?

Is it true that the fd00::/8 address space (User Local Addresses) in IPv6 is for machines that you NEVER want to speak with anything on the Internet? Not exactly. The IPv6 proponent's idea was that ...
Peter Green's user avatar
  • 13.3k
7 votes
Accepted

Need help understanding how packets travel across the internet

You need to look at the layers as each having its own mission. The network layer is - as you wrote - end-to-end. Its addresses have global meaning (within the scope of the entire network). ...
Zac67's user avatar
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