1 00:00:07,650 --> 00:00:13,680 Okay, so let's see if we can answer the questions in this scenario we've been told that PC 1 pings 2 00:00:13,680 --> 00:00:20,190 PC 2 and we need to answer these questions based on the Echo request message sent from PC 1 3 00:00:20,190 --> 00:00:21,750 to PC 2. 4 00:00:22,020 --> 00:00:28,290 So we firstly ask, What is the destination MAC address in the frame at point A in the network when 5 00:00:28,290 --> 00:00:36,970 traffic is sent from one layer to a network across a router the PC is gonna ARP for the routers MAC address 6 00:00:37,420 --> 00:00:45,980 and encapsulate the frame with the routers MAC address when sending traffic to a remote destination? 7 00:00:46,090 --> 00:00:54,580 So the MAC address that will be used is the MAC address of the routers gigabit 000 interface which 8 00:00:54,580 --> 00:00:57,270 is configured as this. 9 00:00:57,280 --> 00:01:03,560 So the answer to the question is E router 1 gigabit 10 00:01:03,630 --> 00:01:14,680 00 MAC address. So I would say for Question 1, the answer is E but let's verify that by using simulation 11 00:01:14,680 --> 00:01:21,730 mode in Packet Tracer, I'm gonna edit my filters to only show ARP and ICMP traffic. 12 00:01:21,730 --> 00:01:29,680 You can click this option show all and then uncheck the various traffic types that you want to view. 13 00:01:33,540 --> 00:01:34,750 On PC 1 14 00:01:34,830 --> 00:01:44,490 I'm gonna send a ping to the IP address of PC 2 and in the output here I'll be able to view the 15 00:01:44,490 --> 00:01:56,870 ICMP traffic, So the inbound PDU shows us that the destination MAC address is the routers MAC address 16 00:01:58,210 --> 00:02:00,920 which is configured as follows. 17 00:02:00,940 --> 00:02:05,830 So again answer to Question 1, is the routers gigabit 18 00:02:05,840 --> 00:02:13,600 000 address is the MAC address used as the destination MAC address in the frame. 19 00:02:14,610 --> 00:02:27,840 And that address is this, so that would be the answer for question 2 which is asking us for the destination 20 00:02:27,840 --> 00:02:29,170 MAC address. 21 00:02:29,280 --> 00:02:33,010 Question 3 asks us what is the encapsulation used. 22 00:02:33,030 --> 00:02:45,920 Notice the encapsulation is Ethernet 2. So Eth 2 is the encapsulation used at point A in the network 23 00:02:46,370 --> 00:02:51,880 we can see that again in the packet tracer capture. 24 00:02:51,950 --> 00:03:05,750 We're then asked to do something similar at point B in the network so I'll click capture forward we could 25 00:03:05,750 --> 00:03:15,040 actually look at that on the frame on the switch and look at the outbound PDU, notice the destination 26 00:03:15,040 --> 00:03:19,590 MAC address is the same, ether type is Ethernet2. 27 00:03:19,780 --> 00:03:28,930 This is the MAC address of the router so the answers here would be very similar. 28 00:03:28,930 --> 00:03:39,640 We're not asked in this example for the encapsulation used but the encapsulation used is ether 2 so 29 00:03:39,640 --> 00:03:40,700 we could look at that here 30 00:03:40,810 --> 00:03:51,040 or we could look at the inbound PDU on the router and you'll notice it has the same information. 31 00:03:52,880 --> 00:03:55,320 So that's the answers to questions 32 00:03:55,490 --> 00:04:04,510 1 to 5. We then need to answer the question, What is the destination MAC address at point C in the 33 00:04:04,510 --> 00:04:05,850 network? 34 00:04:05,890 --> 00:04:15,890 In other words over here, so looking at the outbound PDU what you'll notice is there is no MAC address. 35 00:04:15,890 --> 00:04:24,620 The encapsulation used on the serial interface is HDLC, HDLC doesn't use MAC addresses, MAC addresses 36 00:04:24,620 --> 00:04:39,120 are used in Ethernet so we could see that here or as the inbound PDU on router 2, inbound PDU show 37 00:04:39,120 --> 00:04:41,050 something very similar. 38 00:04:41,050 --> 00:04:52,390 Notice the encapsulation used is HDLC there is no MAC address so the answer to Question 6 is there 39 00:04:52,400 --> 00:05:02,950 is no MAC address at point C in the network and the encapsulation used is HDLC. 40 00:05:03,050 --> 00:05:07,580 We then asked similar information at pointed D in the network. 41 00:05:07,610 --> 00:05:09,830 So what is the destination MAC address. 42 00:05:09,860 --> 00:05:17,210 What is the actual MAC address and what is encapsulation used at point D? 43 00:05:19,100 --> 00:05:23,860 So D is over here so we could look at the routers outbound PDU. 44 00:05:26,530 --> 00:05:39,340 MAC address is this, that is the MAC address of the PC, So IP config shows us the IP address of the 45 00:05:39,370 --> 00:05:50,170 PC, IP config, slash all shows us the destination MAC address of the PC. 46 00:05:50,370 --> 00:05:54,270 So this is the actual MAC address used 47 00:05:58,420 --> 00:06:05,230 going back to our questions. 48 00:06:05,460 --> 00:06:14,430 We need to specify whose MAC address is in the destination frame at point D that is PC 2s MAC address. 49 00:06:14,430 --> 00:06:21,840 This is the actual MAC address and we're back on Ethernet which means it's going to be Ethernet 2 50 00:06:21,960 --> 00:06:32,150 the encapsulation, we can verify that by looking at the outbound PDU on the router notice its Ethernet 51 00:06:32,330 --> 00:06:34,510 2. 52 00:06:34,650 --> 00:06:44,490 So this is gonna be Ethernet 2 once again we could also if we wanted to look at the ingress traffic 53 00:06:44,940 --> 00:06:55,280 on the switch. Ingress shows something very similar destination MAC address frame type is Ethernet 2 54 00:06:58,520 --> 00:07:10,050 that's actually gonna be the same on this link, so on E we could either look at the packet outbound 55 00:07:10,080 --> 00:07:23,940 on the switch notice, it's the same or we could look at the ingress PDU on the PC exactly the 56 00:07:23,940 --> 00:07:34,420 same information is shown for these questions. So if we look at point E the answer to the question will 57 00:07:34,420 --> 00:07:47,850 be the same its PC 2s MAC address, MAC address is that and the frame type is Ethernet 2. So were you 58 00:07:47,850 --> 00:07:54,090 able to answer those questions and can you answer the questions for the return traffic. 59 00:07:54,090 --> 00:08:03,330 In other words the echo reply, so if I click capture forward now notice we're getting an echo reply message. 60 00:08:03,330 --> 00:08:11,670 So if we look at the inbound PDU and we scroll down the type here is this. 61 00:08:11,970 --> 00:08:13,080 But if I go back 62 00:08:16,280 --> 00:08:30,120 the inbound PDU on the PC had a type of 8, so echo request and then the echo reply message over 63 00:08:30,120 --> 00:08:30,660 here 64 00:08:34,030 --> 00:08:36,070 has an ICMP type of this. 65 00:08:36,820 --> 00:08:46,240 And notice you can see that the source MAC address is PC 2 but the destination MAC address is 66 00:08:46,310 --> 00:08:49,920 router 2, so on router 2 67 00:08:52,790 --> 00:08:55,290 show run, notice 68 00:08:55,320 --> 00:09:03,510 this is the MAC address configured on gigabit 000 and that's the MAC address that we see as the destination. 69 00:09:03,780 --> 00:09:08,790 At this point for the Echo reply, source MAC address is this. 70 00:09:09,090 --> 00:09:18,450 Let's work through the process when it gets to the router, the router will see that information on the 71 00:09:18,480 --> 00:09:23,900 inbound PDU destination MAC address is itself. 72 00:09:23,910 --> 00:09:32,960 Source is the PC but on outbound, there are no MAC addresses a different encapsulation is used. 73 00:09:33,030 --> 00:09:38,070 Encapsulation is HDLC but notice the IP address information stays the same. 74 00:09:39,140 --> 00:09:53,080 If we go across the link look at Router 1, inbound PDU is HDLC, outbound PDU is Ethernet 2 destination 75 00:09:53,080 --> 00:10:04,680 MAC address is PC 1 if I look at the config of PC 1 notice that is the MAC address of PC 1 source 76 00:10:04,680 --> 00:10:16,850 MAC address is the router with this MAC address capture forward it'll be the same on the switch, inbound 77 00:10:16,850 --> 00:10:21,410 and outbound PDUs will show that the destination MAC address is 78 00:10:21,410 --> 00:10:25,880 PC 1, source MAC address is the router 79 00:10:25,880 --> 00:10:27,140 same for outbound. 80 00:10:27,140 --> 00:10:35,400 So in and out we'll have that and if we capture forward again we'll see something similar on the 81 00:10:35,400 --> 00:10:46,350 PC for the inbound PDU destination is the PC source is the router. So Packet Tracer allows you to 82 00:10:46,680 --> 00:10:50,440 see the life of a packet quite nicely. 83 00:10:50,610 --> 00:10:58,170 At every stage in the network, it's important that you understand encapsulations source and destination 84 00:10:58,170 --> 00:11:05,310 MAC addresses and how are they used for the CCNA exam. I hope you enjoyed this video. 85 00:11:05,310 --> 00:11:10,020 If you did please like it and please subscribe to my YouTube channel. 86 00:11:10,020 --> 00:11:11,970 I wanna wish you all the very best.