1 00:00:11,100 --> 00:00:16,110 In this video we are trouble shooting network connectivity problems. 2 00:00:16,240 --> 00:00:24,280 We've been told in this scenario that one which is a viral router running ingenius three is not able 3 00:00:24,280 --> 00:00:31,090 to ping the loopback of viral rodded T with the loopback of quadruple fall. 4 00:00:31,230 --> 00:00:32,260 And that's true. 5 00:00:33,440 --> 00:00:44,540 Show IP brought shows us that we only have a connected and local network in the writing table show IP 6 00:00:44,540 --> 00:00:53,060 protocols shows us that we are running the P.F. rotting protocol and it's enabled on all interfaces 7 00:00:53,070 --> 00:01:00,260 on the router show IP OSPF neighbor shows us that we have a full relationship with a neighboring router 8 00:01:00,650 --> 00:01:10,510 with IP address 10 1 to 1 which is this Rotto 1 Rodda so on brought a one show IP always. 9 00:01:10,570 --> 00:01:19,730 NEIGHBOR We only have a neighbor relationship to tend up one but wondered one the on the left that's 10 00:01:19,750 --> 00:01:20,860 on interface first. 11 00:01:20,880 --> 00:01:33,130 Ethan It was 0 0 0 IP protocols OSPF is enabled on the router and is enabled on all interfaces so IP 12 00:01:33,130 --> 00:01:41,950 OSPF interface brief we have SPF enabled on the serial interface and the Fosset Ethan an interface can 13 00:01:41,950 --> 00:01:43,840 you see the problem. 14 00:01:43,840 --> 00:01:47,440 Notice the state of the serial interface is down. 15 00:01:47,560 --> 00:01:56,650 So show IP interface brief we can see that the serial interface is up or down. 16 00:01:56,730 --> 00:01:59,800 Something wrong with the serial interface. 17 00:02:00,120 --> 00:02:04,090 So run interface serial to slash a 0. 18 00:02:04,260 --> 00:02:11,550 Shows us that an IP address is configured on the serial interface but the interface is no shut. 19 00:02:11,550 --> 00:02:14,110 In other words it's of up. 20 00:02:14,250 --> 00:02:15,410 Nothing else is shown. 21 00:02:15,420 --> 00:02:18,630 So show interface serial to slash zero. 22 00:02:18,690 --> 00:02:25,800 We can see that the interfaces up down we can see the encapsulation keepalive is set to 10 seconds 23 00:02:28,620 --> 00:02:37,880 to show IP was P.F. interface brief we can see once again that OSPF is enabled on the serial interface 24 00:02:38,310 --> 00:02:47,350 but the neighbor relationship is down show IP interface brief interface is up or down. 25 00:02:47,370 --> 00:02:57,080 So this interface has not been administratively shut down show interface Ciril to slash zero. 26 00:02:57,190 --> 00:02:59,200 Can you see the problem. 27 00:02:59,200 --> 00:03:01,690 What's wrong in this output. 28 00:03:03,550 --> 00:03:14,400 Notice here and kept solution HGL see on the side encapsulation Peepy show run interface to slash zero. 29 00:03:14,650 --> 00:03:19,850 We can see that the site has been set to use peepin kept solution. 30 00:03:20,350 --> 00:03:31,870 So we need to either set it to use HGL C which is the default on Cisco serial interfaces or we need 31 00:03:31,870 --> 00:03:42,520 to set the encapsulation to people on both sides so set the encapsulation to H.M.S. show IP interface 32 00:03:42,850 --> 00:03:43,480 brief 33 00:03:46,540 --> 00:03:55,180 interfaces up and down but notice that schist come up and notice the OSPF relationship has gone to full 34 00:03:56,160 --> 00:04:07,020 so on a one show IP SPF neighbor notice we now have two neighbor relationships one two Rodda two across 35 00:04:07,080 --> 00:04:16,720 the several interface and one to this Iowas Virata on the left using the fast ethernet interface. 36 00:04:16,780 --> 00:04:18,240 So that looks a lot better. 37 00:04:18,450 --> 00:04:22,650 Let's have a look at the writing table of Rotto one which is viral. 38 00:04:22,690 --> 00:04:24,390 I was Virata. 39 00:04:24,390 --> 00:04:30,330 We now see the loopback quadruple for the writing table. 40 00:04:30,450 --> 00:04:32,560 So can we paying that loop back. 41 00:04:32,580 --> 00:04:34,250 Yes we can. 42 00:04:34,370 --> 00:04:45,140 We're going to disable IP domain look up to speed up tracing So Trace could fall. 43 00:04:45,320 --> 00:04:51,620 The trace shows us the path that goes to the Strutter one with the search interface to write it to with 44 00:04:51,640 --> 00:05:01,500 a serial interface and then on to the I was the router with the loopback quadruple for now to prove 45 00:05:01,500 --> 00:05:13,630 that I could do a debug a debug IP ICMP to ping and notice we see the output on the screen of this Rodda. 46 00:05:13,920 --> 00:05:21,970 So be careful when asked to troubleshoot a broadening protocol such as I was P.F. in the CCN exam. 47 00:05:22,080 --> 00:05:29,010 The issue could be unrelated to OSPF the issue could be an interface that's been mis configured in this 48 00:05:29,010 --> 00:05:32,210 example the encapsulation was incorrect. 49 00:05:32,280 --> 00:05:38,580 You have to have either HPLC on both sides or PDP on both sides of a serial link. 50 00:05:38,730 --> 00:05:42,090 A mismatch caused the interface to go up or down. 51 00:05:42,150 --> 00:05:48,240 In other words the interface was administratively up but the line protocol was down which caused an 52 00:05:48,240 --> 00:05:53,520 issue with broad exchange and advertisement which meant that we couldn't send traffic from the left 53 00:05:53,520 --> 00:05:57,520 hand side of the network to the right hand side of the network. 54 00:05:57,780 --> 00:06:03,100 If you enjoyed the video please like it please subscribe to my YouTube channel. 55 00:06:03,180 --> 00:06:04,700 I wish you all the very best.