1 00:00:00,530 --> 00:00:04,130 Ethernet ten based two uses coaxial cable. 2 00:00:04,160 --> 00:00:11,090 The specifications are different to the coaxial cable used in cable television, but the point I'm trying 3 00:00:11,090 --> 00:00:20,270 to make is coaxial cable running a base band signal can only transmit or receive a single signal at 4 00:00:20,270 --> 00:00:21,470 any given time. 5 00:00:21,680 --> 00:00:29,030 Broadband uses coaxial cable, but allows for multiple signals to be sent across the wire at any given 6 00:00:29,030 --> 00:00:29,600 time. 7 00:00:29,870 --> 00:00:36,860 Ethernet uses base band signaling, in other words, ten base two or ten base five in the past. 8 00:00:36,860 --> 00:00:40,280 So in ten base two coaxial cable was used. 9 00:00:40,400 --> 00:00:44,360 BNC connectors were used to connect devices to the network. 10 00:00:44,480 --> 00:00:48,980 A, B and C, RT Connector would connect the cable to the PC. 11 00:00:49,430 --> 00:00:51,340 Don't worry too much about this. 12 00:00:51,350 --> 00:00:56,780 This is just a bit of history so that you can understand why things are done in certain ways today. 13 00:00:56,930 --> 00:01:02,690 What's important to realize is that a single piece of cable would have banked connectors, which would 14 00:01:02,690 --> 00:01:05,750 allow you to connect devices to a single cable. 15 00:01:05,780 --> 00:01:12,410 Multiple devices were connected across a single cable, and at the end you would have terminators to 16 00:01:12,410 --> 00:01:14,520 stop signals bouncing back. 17 00:01:14,540 --> 00:01:17,240 And here's an example of a Terminator. 18 00:01:17,540 --> 00:01:24,380 So what a Terminator did is essentially terminate the signal or destroy the signal when it got to the 19 00:01:24,380 --> 00:01:25,510 end of the wire. 20 00:01:25,520 --> 00:01:30,780 So when the signal is sent across the wire, it shouldn't bounce back and cause collisions. 21 00:01:30,800 --> 00:01:36,020 So the Terminator would terminate the signal to ensure that it didn't bounce back. 22 00:01:36,170 --> 00:01:39,800 Once again, the reason for doing this is because base band is used. 23 00:01:39,800 --> 00:01:46,970 Base band only allows a single signal to be sent across the wire or cable at any time. 24 00:01:47,270 --> 00:01:51,250 So we couldn't have a signal bouncing back and causing a collision. 25 00:01:51,260 --> 00:01:53,180 Hence Terminators we used. 26 00:01:53,810 --> 00:01:58,640 Now, before we continue discussing the transmission of data in more detail, let's talk about what 27 00:01:58,640 --> 00:01:59,990 a mac address is. 28 00:02:00,440 --> 00:02:08,389 A media access control address or MAC address, also called a physical address, is a unique identifier 29 00:02:08,419 --> 00:02:10,449 assigned to network interfaces. 30 00:02:10,460 --> 00:02:16,370 A mac address is a layer two address, identifying a network interface card or NIC. 31 00:02:16,490 --> 00:02:19,550 It is typically built in by the manufacturer. 32 00:02:19,550 --> 00:02:28,550 In other words, it's burnt in to the network card by the NEC manufacturer and it's 48 bits in length. 33 00:02:28,700 --> 00:02:31,880 The 48 bits are divided into two portions. 34 00:02:32,000 --> 00:02:38,030 The UI portion is 24 bits in length and the station addresses also 24 bits in length. 35 00:02:38,030 --> 00:02:48,830 The UI or organizational unique identifier identifies a vendor such as Cisco or HP or Dell or other 36 00:02:48,830 --> 00:02:54,020 vendors that manufacture network devices or PCs or servers. 37 00:02:54,410 --> 00:03:02,150 Each manufacturer is assigned an O UI, and each vendor in turn can create and assign end station addresses 38 00:03:02,150 --> 00:03:03,950 to network interface cards. 39 00:03:04,160 --> 00:03:07,040 The station addresses should be unique. 40 00:03:07,130 --> 00:03:13,730 Now, I say should be unique because there have been cases where addresses have been duplicated by manufacturers. 41 00:03:14,000 --> 00:03:19,460 So you may end up having a network with duplicate MAC addresses, which causes a lot of problems in 42 00:03:19,460 --> 00:03:20,930 an Ethernet environment. 43 00:03:21,170 --> 00:03:27,920 In an Ethernet environment, on a segment or a piece of cable, we're assuming that all devices have 44 00:03:27,920 --> 00:03:29,420 a unique Mac address. 45 00:03:29,810 --> 00:03:33,950 It's also possible in software to change device MAC addresses. 46 00:03:33,950 --> 00:03:40,430 So on my interface card as an example, I can go to properties, go to configuration. 47 00:03:41,080 --> 00:03:48,670 Selected once I can then go to locally administrated addresses and then I can change the value so I 48 00:03:48,670 --> 00:03:50,530 could make it quadruple a. 49 00:03:50,710 --> 00:03:51,850 Quadruple B. 50 00:03:52,610 --> 00:03:54,170 Quadruple C and click. 51 00:03:54,170 --> 00:03:54,800 Okay. 52 00:03:56,080 --> 00:04:03,610 Opening a cmd prompt and typing IP config forward slash all and then scrolling up I'll be able to see 53 00:04:03,610 --> 00:04:07,510 that my physical Mac address is now set to ABC. 54 00:04:08,210 --> 00:04:15,740 I've just changed my Mac address from the Burnt Inn address set by the manufacturer to something else. 55 00:04:15,770 --> 00:04:22,850 Now, if I did that on multiple PCs or multiple devices, I would be causing an issue with duplicate 56 00:04:22,850 --> 00:04:23,870 Mac addresses. 57 00:04:24,110 --> 00:04:30,800 So once again, the first portion of a mac address is the O UI, and the second portion is a unique 58 00:04:30,800 --> 00:04:33,440 value assigned by the manufacturer. 59 00:04:33,950 --> 00:04:36,980 So on my network card, I'll set it back to the default. 60 00:04:39,970 --> 00:04:46,990 So now when I run IP config forward slash all notice the built in mac address on my local area. 61 00:04:46,990 --> 00:04:52,060 Connection uses the unique value assigned by the manufacturer. 62 00:04:52,420 --> 00:04:54,790 Wireshark has a nice tool to look at. 63 00:04:54,790 --> 00:04:56,080 Oh UI codes. 64 00:04:56,200 --> 00:05:03,540 So I've just added 0001e6 and that should list the manufacturer for that Mac address. 65 00:05:03,550 --> 00:05:05,500 In this case you can see it's HP. 66 00:05:05,890 --> 00:05:11,260 So Mac addresses that start with 0001e6 or HP Mac addresses. 67 00:05:11,740 --> 00:05:16,240 I can also look on the Triple E website to see similar information. 68 00:05:16,240 --> 00:05:21,730 Notice that both E6 and E seven codes are manufactured by HP. 69 00:05:21,760 --> 00:05:28,420 There's a long list of different UI codes and you'll be able to see which O UI codes are associated 70 00:05:28,420 --> 00:05:29,920 with which vendor.