1 00:00:09,330 --> 00:00:17,430 This is one of multiple videos discussing Dynamic Host Configuration Protocol or DGP and specifically 2 00:00:17,700 --> 00:00:19,890 how to troubleshoot DHC. 3 00:00:20,430 --> 00:00:27,780 In this typology we've got a client connected to a router connected to a DHP server and we've been told 4 00:00:27,780 --> 00:00:32,460 that the client is not receiving IP addresses from the DHP server. 5 00:00:32,790 --> 00:00:43,590 In this example rather than using physical PCs I've got us V-Rod is acting as DHP server and DHP client 6 00:00:44,640 --> 00:00:53,800 so he has the client show IP interface brief noticed the client hasn't got an address assigned to Gigabit 7 00:00:54,010 --> 00:01:06,040 00 DHB is being used but no address has been assigned so let's shut the interface down and then no shut 8 00:01:06,040 --> 00:01:08,000 it to test. 9 00:01:08,040 --> 00:01:09,070 What's happening. 10 00:01:11,030 --> 00:01:20,640 Interfaces come up show IP interface brief interfaces up no address has been assigned through DHP. 11 00:01:20,960 --> 00:01:32,140 So on the DHP server we're trying to debug a debug IP DHP server and I'm going to go for packets to 12 00:01:32,140 --> 00:01:34,680 see detailed information. 13 00:01:34,870 --> 00:01:45,050 We are already seeing something here says Cline's VPN is something no option 1 25 DHP discover received 14 00:01:45,140 --> 00:01:51,270 from a client through a relay of 10 1 1 2 5 4. 15 00:01:51,650 --> 00:02:00,380 So ADHD the message is being relayed by the router we can see in this example that router 2 has the 16 00:02:00,490 --> 00:02:06,620 IP address on the interface facing the client that's the address that we see on the DHP server. 17 00:02:06,880 --> 00:02:11,270 But we told her that option 1.5 is not present in the message. 18 00:02:11,540 --> 00:02:15,320 There's a problem with option 1 25. 19 00:02:15,510 --> 00:02:22,890 You can find information about option 125 in this RAFC vendor identifying vendor options for DHV the 20 00:02:24,130 --> 00:02:25,780 problem here he said. 21 00:02:25,780 --> 00:02:29,320 Option 1 25 is a vendor dependent. 22 00:02:29,430 --> 00:02:36,340 So we've seen a lot of messages stating that option 1 25 is not present in the message. 23 00:02:36,480 --> 00:02:42,670 So let's have a look at the relay agent show run interface gigabit 00. 24 00:02:42,690 --> 00:02:50,770 Now we do see the IP help address on the relay agent which is routed to but we still seeing problems 25 00:02:50,980 --> 00:03:01,220 on the DHP server we're getting information at the DHP server based on this configuration so we can 26 00:03:01,220 --> 00:03:02,750 ping the DHP server. 27 00:03:02,870 --> 00:03:09,990 DHP messages are being forwarded to the server but there's a problem on the DHP server. 28 00:03:10,040 --> 00:03:13,560 So let's have a look at the DHV piece of a configuration. 29 00:03:13,940 --> 00:03:16,460 We have a pool configured. 30 00:03:16,540 --> 00:03:17,680 This looks right. 31 00:03:17,840 --> 00:03:26,390 Network default gateway or default router that needs to be in the same subnet as the interface where 32 00:03:26,390 --> 00:03:28,300 the client is configured. 33 00:03:28,580 --> 00:03:29,880 So that looks right. 34 00:03:29,960 --> 00:03:33,230 DNS server is 10 to one or two to one. 35 00:03:33,800 --> 00:03:37,030 That is the IP address of the DHP server. 36 00:03:37,070 --> 00:03:39,050 So that looks right there. 37 00:03:39,050 --> 00:03:42,470 No excluded addresses in the pool. 38 00:03:42,530 --> 00:03:50,400 So we've got a very basic pool and an IP address configured on the gigabit interface everything else 39 00:03:50,400 --> 00:03:51,940 looks standard. 40 00:03:52,110 --> 00:03:57,770 But I'm going to go through the shop run slowly to see if you can find the problem. 41 00:03:57,870 --> 00:04:02,540 What is the issue in this configuration. 42 00:04:02,580 --> 00:04:07,770 Post the video if you need to but there's a problem in this config. 43 00:04:08,130 --> 00:04:09,830 Show IP DHV. 44 00:04:09,950 --> 00:04:11,370 P Paul 45 00:04:14,320 --> 00:04:27,700 we have a pool next address to be allocated to 10 1 1 3 shoyu IP DHP binding is an address allocated 46 00:04:27,700 --> 00:04:33,530 to a client somewhere but no address has been allocated to this client. 47 00:04:33,530 --> 00:04:36,690 Now this is something you need to remember for DHP. 48 00:04:36,740 --> 00:04:43,260 Notice what happens when not top show IP route we are told that there's no gateway of last resort. 49 00:04:43,550 --> 00:04:45,800 There's no writing on the DHP server. 50 00:04:46,190 --> 00:04:53,990 The DHP server has to have a route back to the subnet of the relay agent brought it to is receiving 51 00:04:54,080 --> 00:04:58,540 a DHP broadcast on gigabit 0 0. 52 00:04:58,640 --> 00:05:03,270 But the DHB server doesn't know how to get back there. 53 00:05:04,490 --> 00:05:12,440 So notice here it can't get to that subnet because it doesn't have a route in the writing table. 54 00:05:12,590 --> 00:05:22,130 So IP route and I'll simply create a default route and point it to the IP address on Route 2 which is 55 00:05:22,130 --> 00:05:32,030 gigabit to 0 1 so on the client show the interface brief and no IP address is allocated yet. 56 00:05:32,250 --> 00:05:43,310 I'll force this by shutting the interface down and then shutting it show IP interface brief. 57 00:05:43,380 --> 00:05:47,560 Let's see if we get an IP address in now and there we go. 58 00:05:47,580 --> 00:05:51,620 We've just been allocated an IP address by the DHP server. 59 00:05:51,660 --> 00:05:54,870 This address has been allocated to the client. 60 00:05:54,870 --> 00:06:02,850 Now the reason that the binding was shown previously is that the address was allocated previously to 61 00:06:02,850 --> 00:06:05,710 the client and then it broke the network. 62 00:06:05,730 --> 00:06:08,160 So the same address has been allocated back to the client. 63 00:06:08,160 --> 00:06:15,470 Now since we fixed the network so this is the thing about DHP service on Cisco. 64 00:06:15,720 --> 00:06:19,580 Make sure that they have a route back to the client. 65 00:06:19,590 --> 00:06:24,900 In other words they need to know how to get to the relay agent's IP address. 66 00:06:24,900 --> 00:06:30,210 Otherwise they will not allocate addresses to clients. 67 00:06:30,730 --> 00:06:34,280 So no we have a default route. 68 00:06:34,450 --> 00:06:39,240 And if we look at the binding we should be able to paying the client. 69 00:06:39,580 --> 00:06:42,730 And there you go making paying 10 1 1 2. 70 00:06:43,120 --> 00:06:46,390 So that was an example of how to troubleshoot to DHP. 71 00:06:46,390 --> 00:06:53,070 Don't forget that your DHB servers need Roths back to the relay agents in your typologies. 72 00:06:53,210 --> 00:06:59,860 You found this video useful if it's been of benefit to you please like at least describe to my YouTube 73 00:06:59,860 --> 00:07:00,600 channel. 74 00:07:00,760 --> 00:07:02,350 I wish you all the very best.