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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 should not be using, and it would work in their local network. However, it won't work on the Internet. Their upstream networks providing them connectivity should ...


25

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 interconnecting link for traffic to and from the other ISP no dependency on the IXP, an IXP connects two ISPs on their switch(es), you're not suffering from any outages ...


25

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 accordingly, IP addresses. Different interfaces often have different functions, so it's important to distinguish between them (e.g. internal console, public ...


21

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 unicast routing, and all the routers in the path of the multicast packets need to have multicast routing configured.


19

This can introduce a number of problems, like additional attenuation or cross talk. Splicing is to be avoided whenever possible, but I have seen this work in a pinch although I would never recommend it. They key is to use a cable certification tester (not just a continuity tester) to make sure it still passes your required standard (Cat5/5E/6) after ...


17

I think your study guide is a little outdated. Currently we are at about 500k routes on the Internet. Geoff Huston is collecting stats weekly. You can find his reports here. If you want to see for yourself goto http://www.routeviews.org/ and get access to some real systems on the internet.


17

TCP/IP sockets establish an end-to-end connection through the network, between two specifically addressed end points. BGP uses TCP/IP to communicate between routers (any devices exchanging routing information.) The information exchanged is used by the BGP peers, to better choose the way they choose where to send, (aka, next-hop) packets that they need to ...


14

No. That said, let's see a simplified example: 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 is connected to the internet, and the last one is connected to a network of virtual computers. Let's say I have just one address, 10.1.2.3, and ...


14

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 five RIRs blocks of addresses, and the RIRs assign blocks of addresses from those to businesses that can prove they need them and are willing to pay for them. ...


13

Routing protocols do not "achieve" L3 connectivity. They populate the routing (forwarding) table of the router with information learned from other routers. BGP is an "application" that runs over TCP/IP. In other words a BGP router uses TCP/IP to communicate with other BGP routers to exchange routing information. In order for BGP to work, you must ...


13

This RFC explains the DNS system http://www.ietf.org/rfc/rfc1035.txt. And most importantly, the section "3.5. IN-ADDR.ARPA domain" explains how these names are set for reverse lookup of the IP addresses. So yes, for intermittent hosts which are probably routers, one can set these to pretty much random names and these would turn up in the X.Y.Z.W.IN-ADDR....


12

EDIT: I forgot to mention this - if you're interested, there have been books written about this topic. I highly recommend Bill Norton's The Internet Peering Playbook. Available in print or digital copies - it's pretty much the de facto text on this kind of stuff. DISCLAIMER: The examples used here are hypothetical only - I have zero insight into the ...


12

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 a world wide recognized "brand" company. In fact, I have seen this more often in business settings than university settings (largely due to the fact that more ...


11

There is no conversion, what you have is Encapsulation Ex: you use wireshark on your local PC to capture your HTTP session. Basically, what you end up with looks like: [Ethernet Frame [IP Packet [TCP Segment [HTTP Request]]]] The Ethernet frame has the EtherType field of 0x0800 that gives us the encapsulated protocols as IP The IP Packet has the Protocol ...


10

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 across their domain boundary (i.e. across an Internet). How ? Essentially, to forward multicast packets within your own domain (or Autonomous System, AS), you use ...


9

In addition to the good answers already given by Jens Link and Ron: There's no absolute, objective answer how many routes are active on the internet. The number constantly changes due to networks connecting and disconnecting, routers having outages, etc. Some prefixes are announced only to specific other networks (e.g. using a no-export community) and are ...


9

The reason for switching to a hex-based representation is twofold: They're long enough that using a larger character base is helpful, and in networking in general, a power-of-two base makes calculations simpler for humans since subnet masks are bitmasks. IPv4 addresses are about at the limit of what humans can remember without active memorization techniques,...


9

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 given out by providers to their customers. Small hosting customers will get IPv4 IPs allocated one at a time to their servers. Some organsiations will run ...


9

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 Bluetooth device shall be allocated a unique 48-bit Bluetooth device address (BD_ADDR). The address shall be a 48-bit extended unique identifier (EUI-48) ...


9

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, Global, and ULA, and they can have several of each. Theoretically, there is no real limit to the number of IPv6 addresses you can assign to one interface, although ...


9

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 some awk/python one-liner. If the columns marked AS Number and AS Organization are blank throughout, you need to configure the database for looking these up. ...


8

I think your confusion starts with thinking about 'converting'. No such things happens... IP packets are basic transport units. They have things like a source address and a destination address, and some other bookkeeping stuff, but not much else. And a packet payload of course. UDP or TCP is the next layer. It is in the IP payload. Both UDP and TCP contain ...


8

The PTR record doesn't have to be a valid FQDN. (for internal / non-internet DNS servers, this is not uncommon.) Eg: 1.1.168.192.in-addr.arpa. IN PTR i.saw.a.squirrel.


8

The backbone routers of ISPs (to be precise, Tier-1 ISPs) constitute what is known as the "default-free zone." In this zone, there are no default routes -- every route that is announced on the Internet is carried in the router's route table. It's simply a matter of counting the table entries. If you want to count yourself, you have to arrange a BGP ...


8

Yes. Nobody will advertise any network smaller than a /48. The same thing is in IPv4; no ISP will advertise any network smaller than a /24. The problem is the sheer number of routes that would generate on the Internet by advertising networks smaller than a /48. Even at /48 with the current global address range of 2000::/3, that translates to 35,184,372,...


8

Part 1: Using fiber to run a 1000 foot ethernet link Using fiber to run a long ethernet link is not quite as simple as you make out but it's certainly not unreasonable to DIY. A few things you have missed. Putting connectors on the end of fiber is a specialist job. If you don't want to involve any specialists then you need to buy pre-terminated fiber ...


8

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 RFC Editor for the details. Errata ID: 3485 Status: Verified Type: Technical Reported By: Markus Falb Date Reported: 2013-02-18 Verifier Name: ...


8

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 some of your QoS markings and policies. (I know Verizon Business, among others, has some specific packages for QoS, and you may need to adjust your policies ...


8

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 following best practices then there will be filters in place and the advertisements won't get beyond the hijacker's borders. OTOH if their providers and their ...


7

The networks you connect to should set up filters to accept routes from you only if they are "yours" or those of your customer(s). Some ISPs build filters from various databases (RIR or IRR). Not all networks do this. BGP tables (RIB) do contain ASNs. Forwarding tables (FIB) do not. Not necessarily. It depends on your needs. You could also accept just a ...


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