1 00:00:00,920 --> 00:00:07,730 So in summary when a device wants to communicate with a nother device in the same subnet it will send 2 00:00:07,730 --> 00:00:16,190 a broadcast onto the local segment to find the MAC address of the device using the target IP address. 3 00:00:16,190 --> 00:00:20,080 So in this case a sains the frame to the hub. 4 00:00:20,390 --> 00:00:27,290 The hub because it's a multi port repeater will send the frame out of all ports except the port on which 5 00:00:27,290 --> 00:00:28,060 it arrived. 6 00:00:28,130 --> 00:00:36,560 So both the router and hoost see receive the frame Network Interface Cards will only accept unicast 7 00:00:36,650 --> 00:00:44,150 traffic destined to their MAC address or they'll accept broadcast traffic as well as accepting multicast 8 00:00:44,210 --> 00:00:47,880 traffic for multicast addresses that they subscribe to. 9 00:00:48,170 --> 00:00:52,480 The router has a MAC address of g on interface first Ethan 00. 10 00:00:52,610 --> 00:00:59,480 So the router will receive the broadcast and forward the request to Hialeah protocols the Rotto will 11 00:00:59,480 --> 00:01:07,850 be able to see at least three that this is an odd request for IP address 10 1 1 2 but the Rodda in this 12 00:01:07,850 --> 00:01:14,690 example is configured with IP addresses 10 1 one one hundred and 10 1 to 100. 13 00:01:14,690 --> 00:01:20,990 So the ratable drop the frame because the request is not for one of its IP addresses. 14 00:01:21,260 --> 00:01:23,660 Routers do not forward broadcasts. 15 00:01:23,660 --> 00:01:30,710 So this broadcast is not forwarded out of interface Ethan it is 0 1 so the broadcast received by the 16 00:01:30,710 --> 00:01:32,170 Rada is dropped. 17 00:01:32,420 --> 00:01:38,990 The network interface card on PCC will receive the broadcast and see that this is an up request for 18 00:01:38,990 --> 00:01:40,370 its IP address. 19 00:01:40,370 --> 00:01:43,220 So it will then reply with an op reply. 20 00:01:43,340 --> 00:01:50,990 As we've seen in the Why shall capture PCC will update its up cache to show that IP address 10 1 1 1 21 00:01:51,410 --> 00:01:57,530 is associated with MAC address pay and it will then send the frame to the hub. 22 00:01:57,530 --> 00:02:02,300 The Hubble forward the frame out of all ports because it's a multi-port repeater. 23 00:02:02,300 --> 00:02:07,830 The route in this example will receive a frame from the hub but because the destination MAC address 24 00:02:07,830 --> 00:02:14,510 is a and it's not the MAC address of the Rato which is g the rot it will drop the frame. 25 00:02:14,540 --> 00:02:21,380 You will also receive a copy of the frame when it receives the frame it will accept it because the destination 26 00:02:21,380 --> 00:02:22,180 address is a. 27 00:02:22,310 --> 00:02:23,870 And its MAC address is a. 28 00:02:24,020 --> 00:02:31,520 It will then update its up cache with an up entry stating that IP address 10 1 1 2 is associated with 29 00:02:31,520 --> 00:02:32,840 MAC address C.. 30 00:02:33,020 --> 00:02:38,550 So the reply allows a to update its up cash. 31 00:02:38,630 --> 00:02:41,900 At this point no user traffic has been transmitted. 32 00:02:42,110 --> 00:02:49,070 What's happened here is that the devices have simply worked out which MAC addresses are associated with 33 00:02:49,070 --> 00:02:50,560 which IP addresses. 34 00:02:50,690 --> 00:03:00,100 So AA now knows that MAC address C is associated with IP address 10 1 1 2 the pink traffic cannot be 35 00:03:00,100 --> 00:03:06,760 transmitted with a source of MAC address of a which is the local machine destination MAC address of 36 00:03:06,760 --> 00:03:07,550 C.. 37 00:03:07,570 --> 00:03:14,740 In other words PCC the destination MAC address was learned through ARP source IP addresses change dog 38 00:03:14,760 --> 00:03:21,040 wandered one to one destination IP address and that one would wonder too when the hub receives the frame 39 00:03:21,070 --> 00:03:25,680 from PC it will repeat it out of all interfaces except the interface. 40 00:03:25,690 --> 00:03:26,820 It arrived on. 41 00:03:27,010 --> 00:03:33,130 So the router will once again receive the frame but will drop it because its MAC address is G and the 42 00:03:33,130 --> 00:03:36,760 destination MAC address for this frame is c.. 43 00:03:36,760 --> 00:03:43,480 PCC will also receive the traffic and will accept it because the destination MAC address is C and its 44 00:03:43,480 --> 00:03:48,970 local Mac addresses see the late two heads will be stripped and the IP address information will be read 45 00:03:49,120 --> 00:03:51,010 by higher layer protocols. 46 00:03:51,010 --> 00:03:59,950 This is an ICMP echo packet so the PC will reply with an echo reply message C will send the frame to 47 00:03:59,950 --> 00:04:06,760 the hub with a source mac address of see destination MAC address of a EGNOS the MAC address of AA because 48 00:04:06,760 --> 00:04:09,070 of the previous OP's request message. 49 00:04:09,070 --> 00:04:17,020 So it's up cache has a in-tree associating MAC address a with IP address 10 1 1 1 source MAC address 50 00:04:17,020 --> 00:04:18,100 and the frame is c.. 51 00:04:18,160 --> 00:04:24,750 Destination MAC address is a source IP address is 10 1 1 2 destination IP address is 10 1 1 1. 52 00:04:25,000 --> 00:04:30,430 When the frame is received by the hub the Hubble repeated out of all ports except the one on which it 53 00:04:30,430 --> 00:04:31,740 was received. 54 00:04:31,900 --> 00:04:38,370 The Rotto will receive the frame but will drop it because the destination MAC address is not to G. 55 00:04:38,530 --> 00:04:45,070 The local routers MAC address when it receives the frame from the hub it will accept it because the 56 00:04:45,070 --> 00:04:48,420 destination MAC address is a and the PCs MAC addresses. 57 00:04:48,850 --> 00:04:54,460 It will then strip layer 2 headers and forward the information to a higher layer protocols. 58 00:04:54,460 --> 00:04:56,530 In this case it was an echo reply. 59 00:04:56,770 --> 00:04:59,540 So the ping will show a success message. 60 00:04:59,560 --> 00:05:07,430 In other words an echo request was sent to PCC and an echo reply message was successfully received back. 61 00:05:07,470 --> 00:05:13,590 So in my wireshark capture for example I can filter on ICMP messages. 62 00:05:13,690 --> 00:05:21,850 I can see the initial echo request a message sent from my PC to 10 0 0 0 2 4 4 and I can then see the 63 00:05:21,850 --> 00:05:23,830 echo reply message. 64 00:05:23,830 --> 00:05:28,380 Notice please that these are a unique cost frame's unicast. 65 00:05:28,390 --> 00:05:36,280 Firstly from my PC to the local router and then a unicast from the router to my local machine the same 66 00:05:36,280 --> 00:05:43,000 information would be displayed if you are pinging another local device on the segment as a user you 67 00:05:43,000 --> 00:05:45,010 would see something similar to this. 68 00:05:45,190 --> 00:05:49,970 Ping 10 0 0 2 4 4 and the ping was successful. 69 00:05:50,020 --> 00:05:56,890 So in this example my PC successfully got a reply from the remote device that I was pinging.