1 00:00:19,940 --> 00:00:25,280 In question 5 we we're told to assume that one MAC address is empty. 2 00:00:25,870 --> 00:00:37,090 We can verify that by looking at the output of the show MAC address table command on the switch as we 3 00:00:37,090 --> 00:00:39,500 can see here the MAC address table is empty. 4 00:00:40,400 --> 00:00:48,310 We asked when P.S. five pings P.S. eight what type of packet is sent to the switch initially. 5 00:00:48,580 --> 00:00:50,100 And can we prove it. 6 00:00:50,380 --> 00:00:50,950 So 7 00:00:53,620 --> 00:01:01,000 IP config on P.S. 5 shows us the IP address of P.S. 5 10 1 1 5. 8 00:01:01,270 --> 00:01:02,150 P.S. 8 9 00:01:04,720 --> 00:01:08,630 has IP address 10 1 1 8. 10 00:01:08,690 --> 00:01:15,430 So what kind of frame or what kind of packet is sent to the switch when using terms such as frames and 11 00:01:15,430 --> 00:01:25,070 packets once again are we referring to layer 2 or Layer 3 or Layer 4 of the other side model. 12 00:01:25,090 --> 00:01:32,720 So what I'll do on P.S. 5 is paying 10 1 1 8 before I do that. 13 00:01:32,750 --> 00:01:35,960 Notice the OP cache is empty. 14 00:01:35,960 --> 00:01:41,880 On P.S. 5 if it had just a rebooted the OP cache would be empty. 15 00:01:41,920 --> 00:01:49,580 Something to send two pings into the network we can see that the first packet that was generated is 16 00:01:49,580 --> 00:01:59,780 an all package looking at the actual packet or frame we can see that add layer to the frame has a destination 17 00:01:59,780 --> 00:02:01,100 address of a broadcast. 18 00:02:02,130 --> 00:02:10,530 That type of package at least 3 is OP so in the Layer 3 headers we can see that this is an off packet 19 00:02:11,460 --> 00:02:23,840 requesting the MAC address of host with IP address 10 1 1 8 so the Ethernet type is 0 6 0 8 0 6. 20 00:02:23,860 --> 00:02:28,280 In other words it's an op packet capture forward 21 00:02:31,200 --> 00:02:43,360 and before I continue the answer to Question 5 is this is an op packet it's a broadcast packet we can 22 00:02:43,360 --> 00:02:51,100 see that again by looking at the inbound PD you honor the switch notice destination address is a broadcast 23 00:02:52,190 --> 00:03:00,170 who receives the packet because it's a broadcast it's going to be flooded to the other devices in the 24 00:03:00,170 --> 00:03:09,970 network and then P.S. 6 and P.S. 7 are going to drop it because of the packet is not destined to them. 25 00:03:09,970 --> 00:03:12,650 So the answer for question 6 is. 26 00:03:12,700 --> 00:03:20,860 P.S. 6 P.S. 7 and PCH will receive the packet. 27 00:03:20,970 --> 00:03:22,400 Now here's where things change. 28 00:03:22,410 --> 00:03:26,140 Who receives the you return packet. 29 00:03:26,160 --> 00:03:33,450 So here we've got our op reply on the inbound PD U to the switch. 30 00:03:33,450 --> 00:03:37,290 We can see that the target mac address is this. 31 00:03:37,440 --> 00:03:43,330 That's the MAC address of P.S. 5. 32 00:03:43,420 --> 00:03:48,290 So the MAC address is actually written into the frame. 33 00:03:48,310 --> 00:03:54,120 This is a unique cost packet center from P.S. 8 to P.S. 5. 34 00:03:54,220 --> 00:03:59,790 It's not a broadcast unlike the OP request to notice what happens now. 35 00:04:01,930 --> 00:04:05,790 The packet is only sent to P.S. 5. 36 00:04:05,860 --> 00:04:16,960 It's not flooded out of all ports so the only piece that receives it is P.S. 5 that is different to 37 00:04:16,960 --> 00:04:27,460 our previous example where P.S. One P.S. 2 and P.S. 3 received the return traffic and notice the difference 38 00:04:27,520 --> 00:04:34,320 in question 8 when Pink traffic is sent from P.S. 5 to PCH who receives it. 39 00:04:34,450 --> 00:04:35,160 So here's 40 00:04:37,720 --> 00:04:51,790 ICMP request or echo request message we can see that it's ICMP destination MAC address is P.S. 8. 41 00:04:51,870 --> 00:04:56,040 Source MAC address is P.S. 5 source IP address is. 42 00:04:56,040 --> 00:05:00,150 P.S. 5 destination IP address is PCH. 43 00:05:00,250 --> 00:05:10,670 So notice now that the packet is only sent to PCH so that's a very different to what we saw when we 44 00:05:10,670 --> 00:05:19,130 were using a hub a switch is different to a hub in that it has a separate collision domain on every 45 00:05:19,130 --> 00:05:30,190 port so when packets are sent from P.S. 5 to PCH they are sent directly between the devices they don't 46 00:05:30,730 --> 00:05:34,270 get flooded to the other pieces in the network. 47 00:05:34,270 --> 00:05:44,080 That is very different to a hub so to prove that what I'll do is populate or the OP cache of P.S. 6 48 00:05:44,660 --> 00:05:45,890 so I'll get it to ping. 49 00:05:46,000 --> 00:05:56,730 P.S. 8 and I'll run this in real time so if we look at to the OP cache of P.S. 6 OP caches populated 50 00:06:01,860 --> 00:06:05,160 the same is true on P.S. 5. 51 00:06:05,410 --> 00:06:06,000 So both. 52 00:06:06,000 --> 00:06:15,180 P.S. 5 and P.S. 6 know the MAC address of PCH I'll change this to simulation mode. 53 00:06:16,410 --> 00:06:21,980 And I'll get both of these pieces to ping PCH 54 00:06:27,060 --> 00:06:30,090 both of them are sending ICMP packets. 55 00:06:30,090 --> 00:06:32,130 They both get sent to the switch. 56 00:06:33,980 --> 00:06:41,170 And notice the first one is sent to PCH and then the second one is sent to PCH. 57 00:06:41,170 --> 00:06:52,490 We don't end up with a collision so the switcher cashes the package and allows the communication and 58 00:06:52,490 --> 00:06:54,300 to show you this in a different way. 59 00:06:54,320 --> 00:07:00,380 What I'll do is get pissy 5 to ping PCH 60 00:07:02,900 --> 00:07:14,140 but get to P.S. six to ping P.S. seven CPC five is pinging pieces eight pieces six is pinging pieces 61 00:07:14,190 --> 00:07:21,920 seven in this case pieces six and needs to ARP for the mac address of P.S. seven. 62 00:07:22,030 --> 00:07:29,960 Notice however that there is no collision taking place. 63 00:07:30,090 --> 00:07:41,520 So now notice the OP cache of pieces 6 is populated with the MAC address of both P.S. 7 and PCH so I'll 64 00:07:41,520 --> 00:07:42,750 run that again 65 00:07:46,310 --> 00:07:49,370 and I need to be in simulation mode to do that. 66 00:07:51,830 --> 00:07:54,770 So they both are sending ICMP packets 67 00:07:57,520 --> 00:07:59,300 these are unit costs. 68 00:07:59,340 --> 00:08:09,780 They are not broadcasts notice of the destination of this frame is P.S. 7 destination of this frame 69 00:08:10,650 --> 00:08:22,860 is P.S. 8 both packets can be sent and received by the switch without interference from the other conversation 70 00:08:25,000 --> 00:08:34,590 so the pieces can communicate now without collisions and they are essentially separated from the other 71 00:08:34,590 --> 00:08:42,900 conversation the conversation between P.S. 5 and P.S. 8 happens independently of the conversation between 72 00:08:42,900 --> 00:08:45,900 P.S. 7 and P.S. 6. 73 00:08:45,930 --> 00:08:49,610 We have 4 collision domains here 74 00:08:53,840 --> 00:09:04,350 a hub is a single collision domain a switch has a collision domain per interface but again if P.S. 5 75 00:09:04,440 --> 00:09:05,730 sent a broadcast 76 00:09:09,950 --> 00:09:11,120 the broadcast 77 00:09:14,540 --> 00:09:20,240 would be forwarded to all devices in the network. 78 00:09:20,240 --> 00:09:21,770 This is a layer to switch. 79 00:09:21,770 --> 00:09:29,810 It's going to flood that broadcast out of all ports so everyone is going to receive the broadcast and 80 00:09:29,870 --> 00:09:35,090 everyone is going to have to reply back to that broadcast. 81 00:09:39,460 --> 00:09:46,220 Packet tracing is not perfect software but it allows you to visually see how traffic flows in the network 82 00:09:46,700 --> 00:09:53,480 and to learn how to answer questions such as these. 83 00:09:53,570 --> 00:10:01,550 So when studying for the CCMA exam you can use packet tracer to learn how traffic flows to learn what 84 00:10:01,550 --> 00:10:08,090 frames look like what packets looked like what segments looked like and it helps you essentially become 85 00:10:08,150 --> 00:10:10,430 a better network engineer. 86 00:10:10,490 --> 00:10:12,890 So were you able to answer these questions. 87 00:10:13,130 --> 00:10:20,360 Do you understand how data flows in a network when you have a switch or when you have a hub. 88 00:10:20,600 --> 00:10:24,920 Make sure that you understand how data flows through networks.