1 00:00:08,870 --> 00:00:15,260 This is one of multiple videos discussing the troubleshooting of Dynamic Host Configuration Protocol 2 00:00:15,620 --> 00:00:18,320 or DHP in this typology. 3 00:00:18,320 --> 00:00:23,850 I've got a U.S. visa router acting as a PC and in Iowa. 4 00:00:23,910 --> 00:00:27,130 Virata acting as a DHP server. 5 00:00:27,590 --> 00:00:34,140 I've also got a router that's simply doing routing from one subnet in the network to another. 6 00:00:34,380 --> 00:00:41,220 We've been told that after the DHB client in the apology he's not receiving an IP address and we need 7 00:00:41,220 --> 00:00:42,990 to troubleshoot the issue. 8 00:00:43,320 --> 00:00:53,250 So let's look at what's going on what Casey has the client show IP interface brief the client is configured 9 00:00:53,250 --> 00:01:02,860 for DHP so gigabit 00 the interface used by the broader to connect to the network is currently up up. 10 00:01:02,900 --> 00:01:09,740 In other words a layer 1 and layer two are working but no IP addresses assigned show run interface gigabit 11 00:01:09,820 --> 00:01:14,610 00 shows us that the interface is configured for DHP. 12 00:01:14,960 --> 00:01:18,680 But once again we are not getting an address assigned. 13 00:01:19,630 --> 00:01:27,070 Let's have a look at it too which is doing interval and writing show IP interface brief we can see that 14 00:01:27,070 --> 00:01:32,380 an IP address is configured on gigabit 00 as well as gigabit 0 1. 15 00:01:32,650 --> 00:01:34,860 Let's have a look at the DHB server. 16 00:01:34,880 --> 00:01:37,610 Show IP interface brief. 17 00:01:37,720 --> 00:01:41,190 This is the IP address of the DHP server. 18 00:01:41,290 --> 00:01:44,590 Can the router paying the DHP server. 19 00:01:44,650 --> 00:01:45,750 Yes it can. 20 00:01:46,570 --> 00:01:53,520 So we can ping from the router to the DHP server show run interface but 00. 21 00:01:53,710 --> 00:01:56,500 Notice this command IP help address. 22 00:01:56,500 --> 00:02:04,690 So that looks that help address is configured to point to the DHP server Let's run a one shot capture 23 00:02:04,700 --> 00:02:10,820 here to see if any DHP messages are being sent to the DHP server. 24 00:02:12,970 --> 00:02:14,890 So I'm capturing on this link. 25 00:02:14,890 --> 00:02:24,510 What I'll do is shut and no shut the interface on the client to get it to request an IP address from 26 00:02:24,600 --> 00:02:33,090 the DHP server that will allow us to see whether the DHP requests are getting to the DHP server. 27 00:02:33,090 --> 00:02:39,180 So NY shock we're seeing a number of DHP messages of full to boot. 28 00:02:39,180 --> 00:02:48,530 P we can see that the router is requesting an IP address on behalf of the client so he has the bootstrap 29 00:02:48,620 --> 00:02:58,490 protocol discover a message client IP address is not configured the relay agent is routed to a show 30 00:02:58,520 --> 00:03:08,120 IP interface brief the Rodda is receiving a DHP discover from the client on this interface and is then 31 00:03:08,120 --> 00:03:10,740 forwarding that to the DHP server. 32 00:03:12,010 --> 00:03:18,570 So we definitely getting DHP discover messages on this link. 33 00:03:18,590 --> 00:03:24,620 Let's do a debug on the DHP service debug IP DHP server. 34 00:03:25,010 --> 00:03:26,840 And let's look at events 35 00:03:29,710 --> 00:03:32,440 force the client to request an address again 36 00:03:35,430 --> 00:03:37,800 OK so something's happening. 37 00:03:38,430 --> 00:03:42,990 Let's stop debugging. 38 00:03:43,190 --> 00:03:46,340 So we're getting a Discover from the client. 39 00:03:46,400 --> 00:03:49,780 So it's definitely being received by the DHP server. 40 00:03:50,120 --> 00:03:56,380 The server is receiving the Discover message but can you see what's wrong in the output. 41 00:03:56,730 --> 00:03:58,460 What's the problem. 42 00:03:58,460 --> 00:03:59,570 Let me give you another hint. 43 00:03:59,570 --> 00:04:03,750 Show IP DHC P pool. 44 00:04:04,010 --> 00:04:05,600 What's the problem. 45 00:04:06,600 --> 00:04:13,430 Can you see the issue in the de-bunk and in the show command OK. 46 00:04:13,450 --> 00:04:18,060 Notice this output we are told that the pool is empty. 47 00:04:18,070 --> 00:04:21,580 Notice this is a problem with the addresses are located 48 00:04:25,830 --> 00:04:29,790 the server is definitely receiving messages. 49 00:04:29,850 --> 00:04:32,080 So we were receiving discovery messages. 50 00:04:32,220 --> 00:04:34,310 There's one address pool available. 51 00:04:35,460 --> 00:04:41,760 OK see if you can see the problem in the running can fake the Rodda. 52 00:04:42,120 --> 00:04:43,350 What's the issue here. 53 00:04:45,350 --> 00:04:52,650 That's IP DHP excluded address 10 1 1 1 to 10 1 1 255. 54 00:04:52,910 --> 00:04:56,490 We've excluded all the addresses from the DHP pool. 55 00:04:56,720 --> 00:05:00,890 So no IP addresses can be allocated to the client. 56 00:05:01,120 --> 00:05:09,830 Show IP DHC pool we have a pool in this range but no addresses are available because we've excluded 57 00:05:09,830 --> 00:05:15,220 them so let's remove the statement 58 00:05:19,650 --> 00:05:29,390 and use the on IPD HGP excluded address 10 1 1 1 2 let's say 10 1 100 show run 59 00:05:32,620 --> 00:05:40,870 extruded addresses are now in this range for the pool notice on the client an address is an assigned 60 00:05:41,110 --> 00:05:43,360 address 101. 61 00:05:43,360 --> 00:05:52,410 So show IP interface brief the client has been allocated an IP address and should hopefully at this 62 00:05:52,410 --> 00:06:00,000 point be able to ping the DHP server which it can be careful with the excluded addresses in the pool. 63 00:06:00,050 --> 00:06:04,670 So show IP DHB P binding. 64 00:06:04,750 --> 00:06:11,050 We now have an address allocated to the client of IP DHP pool. 65 00:06:11,290 --> 00:06:22,200 One address is now least next address to allocate is 10 1 1 1 0 2 noticed previously that the current 66 00:06:22,200 --> 00:06:25,150 index was set to 0.0 0.0. 67 00:06:25,350 --> 00:06:28,840 In other words no addresses would be allocated to clients. 68 00:06:29,310 --> 00:06:34,780 But now the next address that will be allocated is 10 to 1 to 1 2 1 2 2. 69 00:06:35,190 --> 00:06:42,480 So if I change the MAC address on this client to something 70 00:06:45,160 --> 00:06:51,850 like this and then shut the interface down and then no shut it. 71 00:06:52,070 --> 00:07:00,270 What we should see is that the index changes and there you go because the client has been allocated 72 00:07:00,320 --> 00:07:01,670 at this address. 73 00:07:01,810 --> 00:07:04,990 So the next available address is this one. 74 00:07:05,080 --> 00:07:08,270 So that was an example of how to troubleshoot DHP. 75 00:07:08,590 --> 00:07:15,250 I hope you found the video useful if you did please like it please or since I've cried to my YouTube 76 00:07:15,250 --> 00:07:15,950 channel. 77 00:07:16,210 --> 00:07:17,800 I wish you all the very best.