1 00:00:09,560 --> 00:00:13,140 This is one of multiple troubleshooting videos. 2 00:00:13,610 --> 00:00:21,370 We've been told that switch one on the left in this typology is not able to ping switch to ON THE RIGHT. 3 00:00:21,470 --> 00:00:28,570 In this typology now in apology I'm using physical devices rather than three. 4 00:00:28,740 --> 00:00:34,750 I'm only using Janus three to show a diagram of the topology. 5 00:00:34,870 --> 00:00:41,780 So let's verify what we've been told on which one can we ping switch to. 6 00:00:42,190 --> 00:00:43,590 It looks like we can't. 7 00:00:43,630 --> 00:00:47,060 The pings are failing. 8 00:00:47,220 --> 00:00:52,100 So let's do some troubleshooting show IP interface brief. 9 00:00:52,210 --> 00:00:54,230 Can you see the problem here. 10 00:00:54,490 --> 00:00:56,840 What's wrong in this output. 11 00:00:57,680 --> 00:01:02,370 So here's the command to show IP interface brief what's wrong. 12 00:01:02,630 --> 00:01:08,230 Notice fast Ethernet 0 3 is down down show interface. 13 00:01:08,270 --> 00:01:15,180 0 3 we told us that the interfaces down the line protocol is down. 14 00:01:15,360 --> 00:01:17,040 It's not connected. 15 00:01:17,040 --> 00:01:21,470 Now at this point you may need to check the cabling to see if there's a problem. 16 00:01:21,640 --> 00:01:26,320 But before you do that let's have a look at the connection on the other side. 17 00:01:26,560 --> 00:01:31,640 Some brought a one show IP interface brief on the side. 18 00:01:31,690 --> 00:01:36,670 The interfaces up down show interface zero 19 00:01:39,360 --> 00:01:45,510 in the south but we can see that first Ethan at zero is up or down on the side. 20 00:01:45,540 --> 00:01:50,170 First Ethan it is 0 3 is down down. 21 00:01:50,220 --> 00:01:53,580 Now based on this output what's the problem. 22 00:01:53,580 --> 00:01:58,830 Can you see an issue between the switch and the Rodda based on the output. 23 00:01:59,250 --> 00:02:05,400 So before walking and checking the physical cabling or getting someone else to check the physical cabling 24 00:02:06,030 --> 00:02:09,030 What can you see that's wrong in this output. 25 00:02:10,690 --> 00:02:16,680 OK so notice this full duplex or 100 megabits per second on the side. 26 00:02:16,690 --> 00:02:20,230 Notice auto duplex 10 megabits per second. 27 00:02:20,620 --> 00:02:29,230 It looks like there's a problem with the speed and duplex configuration on the side a mac address and 28 00:02:29,230 --> 00:02:34,330 an IP address have been configured on the fast ethernet interface and the speed of the interface is 29 00:02:34,330 --> 00:02:40,710 10 meg on the side and the output we can see that it's using full duplex 100 make the second. 30 00:02:41,020 --> 00:02:47,540 So if we look at the interface configuration notice the speed and duplex have been hard coded. 31 00:02:47,740 --> 00:02:54,370 Typically today you wouldn't do that but let's say for example that we set the speed and duplex to 100 32 00:02:54,370 --> 00:02:54,980 make. 33 00:02:55,210 --> 00:02:57,900 So on the side we set the speed to 100 meg. 34 00:02:58,300 --> 00:03:06,170 Notice you can see that the interface came up and then went down and we are seeing another problem duplex 35 00:03:06,200 --> 00:03:07,410 mismatch. 36 00:03:07,700 --> 00:03:16,110 And we can see that on both sides we are told that first Ethan it is 0 is using half duplex and on our 37 00:03:16,110 --> 00:03:23,440 side we're not using half duplex so show run interface if a zero speed is 100. 38 00:03:23,790 --> 00:03:32,430 What you probably want to do is set this to do or to negotiation rather than hard coded so that they 39 00:03:32,430 --> 00:03:36,420 can negotiate properly and on the side 40 00:03:39,310 --> 00:03:45,310 we probably want to do the same show run interface if zero slash three rather. 41 00:03:45,310 --> 00:03:51,170 So let's set the speed to order and the duplex to order. 42 00:03:51,520 --> 00:03:55,840 So that's automatically negotiated with the other side. 43 00:03:55,840 --> 00:04:01,420 Here we still seeing problems with speed and duplex show run interface f 0. 44 00:04:01,840 --> 00:04:08,360 Everything is set to auto and on the side show run interface 0 3. 45 00:04:08,560 --> 00:04:13,110 Everything is set to Auto Show interface if 0 is than 3. 46 00:04:13,300 --> 00:04:17,080 We can now see that the interface has come up up. 47 00:04:17,080 --> 00:04:18,580 It's connected. 48 00:04:18,580 --> 00:04:19,450 Show interface. 49 00:04:19,470 --> 00:04:25,050 If a zero interface is up up so that looks a lot better. 50 00:04:25,480 --> 00:04:29,170 So it looks like we've solved a problem between switch 1 and router 1. 51 00:04:29,350 --> 00:04:32,190 We didn't have to check the physical cabling. 52 00:04:32,200 --> 00:04:38,870 The problem here was that the speed and the duplex were wrong. 53 00:04:38,880 --> 00:04:43,740 Ok so can switch one ping switch to. 54 00:04:44,130 --> 00:04:46,230 We're still having a problem. 55 00:04:46,230 --> 00:04:47,980 We see us in the output. 56 00:04:48,000 --> 00:04:51,570 In other words unbreachable show running come fake 57 00:04:54,780 --> 00:04:56,630 which doesn't have a lot of config on it. 58 00:04:56,650 --> 00:05:03,520 But what it does have is an IP address configured locally and the default gateway so it can be paying 59 00:05:04,300 --> 00:05:05,400 the default gateway. 60 00:05:05,500 --> 00:05:19,140 Yes we can so disable IP domain look up to speed up trace rot and if we trace to 10 1 3 to notice we 61 00:05:19,140 --> 00:05:23,310 get to 10 1 1 1 but we don't get any further. 62 00:05:23,340 --> 00:05:31,960 So it looks like the traffic gets too broad of one but we're receiving an unreachable message because 63 00:05:32,230 --> 00:05:36,220 one doesn't know what to do with a traffic. 64 00:05:36,440 --> 00:05:39,510 So he has brought a one show IP ROFFT. 65 00:05:39,740 --> 00:05:41,570 Can you see a problem here. 66 00:05:41,660 --> 00:05:46,040 We only have a route for Ethan at zero. 67 00:05:46,160 --> 00:05:51,390 There's no routes to get to such to show IP protocol. 68 00:05:51,520 --> 00:05:58,310 We are running the GOP on the router and it's enabled on all interfaces. 69 00:05:58,450 --> 00:06:07,470 So show run section you GOP has the GOP configuration that looks good. 70 00:06:07,480 --> 00:06:18,910 Show i.p your GOP interface the GOP is enabled on fast Ethernet Zerah as well as serial 0 shows ETP 71 00:06:18,900 --> 00:06:19,940 neighbors. 72 00:06:20,080 --> 00:06:26,020 We see SCDP neighbor relationship to switch one but we don't see SCDP neighbor relationship to switch 73 00:06:26,020 --> 00:06:32,600 to CGP allows us to check laya to connectivity if CTP is working. 74 00:06:32,630 --> 00:06:38,380 It means that layer 1 and layer 2 are working that at the moment it looks like layer 1 and layer 2 are 75 00:06:38,380 --> 00:06:39,700 not working. 76 00:06:40,060 --> 00:06:45,100 So lets check show IP interface brief. 77 00:06:45,270 --> 00:06:46,910 Can you see the problem. 78 00:06:47,080 --> 00:06:49,620 Notice serial is zero. 79 00:06:49,680 --> 00:06:51,470 He's up and down. 80 00:06:51,540 --> 00:07:00,840 There's a problem with the physical link between Rodda one and router to on it to show IP interface 81 00:07:02,390 --> 00:07:03,580 brief. 82 00:07:03,770 --> 00:07:05,630 We have the same problem here. 83 00:07:05,900 --> 00:07:09,000 Serial 0 is up and down. 84 00:07:09,140 --> 00:07:11,210 So now would be a good time to check the cabling. 85 00:07:11,210 --> 00:07:17,810 Fortunately with serial interfaces we can use the command to show controllers serial and specify the 86 00:07:17,810 --> 00:07:23,290 serial interface number to check whether a cable is connected to the router. 87 00:07:23,630 --> 00:07:29,300 In this case interface serial 0 has a DTV cable connected. 88 00:07:29,330 --> 00:07:31,230 It's a thirty five cable. 89 00:07:31,400 --> 00:07:37,720 But notice the problem the clocks are stopped on the side show controllers. 90 00:07:37,740 --> 00:07:42,270 Cereal is zero. 91 00:07:42,320 --> 00:07:44,160 What's the problem here. 92 00:07:44,450 --> 00:07:47,150 What's wrong and how do you fix it. 93 00:07:50,040 --> 00:07:57,960 OK notice here we've got a thirty five DC cable and there's no clocking on the cable show run interface 94 00:07:58,050 --> 00:08:02,940 serial zero clocking hasn't been configured on the cable 95 00:08:05,820 --> 00:08:09,000 on a DTV cable. 96 00:08:09,090 --> 00:08:11,750 You don't use the clock rate command. 97 00:08:12,030 --> 00:08:21,950 So I could specify a clock rate but that command is going to have no effect because this is a DTV cable. 98 00:08:22,350 --> 00:08:30,180 But on this side if we enter the clock rate command and notice there are different clock rates available. 99 00:08:30,240 --> 00:08:40,370 I'm just going to use 64 K show run interface serial 0 noticed the command is retained in the running 100 00:08:40,370 --> 00:08:55,820 config and that's because the interface here is a DC interface so shoyu IP interface brief interface 101 00:08:55,900 --> 00:09:03,030 is now map up on the side we saw a neighbor relationship established in your job. 102 00:09:04,270 --> 00:09:06,810 We also saw the interface come up. 103 00:09:07,150 --> 00:09:10,140 So show IP interface brief. 104 00:09:10,480 --> 00:09:15,340 The interface is now up up show controllers 105 00:09:17,870 --> 00:09:21,590 cereal zero on the side. 106 00:09:21,590 --> 00:09:31,040 We now see that transmit and receive clocks are detected on the side show controllers serial 0 the clucking 107 00:09:31,040 --> 00:09:39,020 is set to 64 kilobits per second because the side is the DC side of the cable a back tabac cable is 108 00:09:39,020 --> 00:09:41,180 connected between Rodda one and router to 109 00:09:44,390 --> 00:09:46,560 and router two is the DC side. 110 00:09:46,580 --> 00:09:51,340 So it needs to provide the clocking for the connection. 111 00:09:51,740 --> 00:10:00,840 So show CGP neighbors we now see router two as a neighbor of one ping ten one to two. 112 00:10:01,010 --> 00:10:03,980 We can ping Rodda to show up at your job. 113 00:10:03,980 --> 00:10:13,450 The neighbor we can see rodded to as a neighbor and hopefully switch one will now be able to paying 114 00:10:13,870 --> 00:10:24,990 switch to which it can to confirm that I'll use the command debug IP ICMP on switch to and ping from 115 00:10:24,990 --> 00:10:28,990 which one to switch to and we can see that an echo reply was sent. 116 00:10:30,940 --> 00:10:34,140 Switch to can also paying switch one. 117 00:10:34,210 --> 00:10:37,990 So we've successfully resolved two issues in this network. 118 00:10:37,990 --> 00:10:40,450 Be careful when troubleshooting. 119 00:10:40,450 --> 00:10:49,120 It's a good idea to know us-I model and split the troubleshooting ping trace route in CGP are useful 120 00:10:49,120 --> 00:10:51,170 for troubleshooting networks. 121 00:10:51,190 --> 00:10:59,810 It's important that you learn your show commands don't just type a show run on a device learn how to 122 00:10:59,810 --> 00:11:09,910 use show commands to see the state of interfaces so as an example here we can see that the interfaces 123 00:11:09,970 --> 00:11:18,280 up will be able to see other information on the interface such as the load packets sent and received 124 00:11:18,280 --> 00:11:19,110 and so forth. 125 00:11:22,220 --> 00:11:29,090 If I removed the clock rate on the interface by using the common clock rate what we should see on Broadway 126 00:11:29,090 --> 00:11:37,670 one is that the interface goes down it stays up for a while because of the keep alive which is set to 127 00:11:37,670 --> 00:11:44,510 10 seconds but after a while as you can see that your GOP neighbor relationship went down and what we 128 00:11:44,510 --> 00:11:50,610 should see is that the physical interface goes down after a while 129 00:11:55,220 --> 00:11:56,030 like that. 130 00:11:56,060 --> 00:11:57,870 So the interface has just gone down. 131 00:11:57,870 --> 00:11:59,900 Show interface 0. 132 00:12:00,230 --> 00:12:02,590 Notice interfaces up down. 133 00:12:02,600 --> 00:12:10,230 So learn to use your show command to see what's going on on the network so show controllers serial zero. 134 00:12:10,220 --> 00:12:16,820 Here we can see that a cable is connected but we're not receiving clocking 135 00:12:19,270 --> 00:12:23,870 clocking a set. 136 00:12:23,900 --> 00:12:27,260 This will change as you can see here transmit and receive. 137 00:12:27,260 --> 00:12:32,890 Clocks are detected interfaces come up show interface serial zero. 138 00:12:32,930 --> 00:12:39,380 We can now see that the interfaces of pop one of the most important skills for use a network engineer 139 00:12:39,790 --> 00:12:42,920 is to learn how to troubleshoot networks. 140 00:12:42,920 --> 00:12:49,070 Hope you found this video useful if it's been of benefit to you please like it temperedly subscribe 141 00:12:49,280 --> 00:12:50,880 to my YouTube channel. 142 00:12:50,900 --> 00:12:52,430 I wish you all the very best.