1 00:00:01,050 --> 00:00:05,580 In this video I'm going to show you how to set up and not overloading or port address translation or 2 00:00:05,710 --> 00:00:14,100 pat these two internal devices Route 1 and of for a going to be enacted to the IP address of router 3 00:00:14,130 --> 00:00:19,460 to the router to configure it on the first East and a 0 1 interface with the IP address. 4 00:00:19,470 --> 00:00:26,100 8. wondered wondered one but rather than allocating additional addresses for Nat I'm going to Knecht 5 00:00:26,400 --> 00:00:33,930 both these devices to that single IP address by using port address translational Pat router 3 in this 6 00:00:33,930 --> 00:00:38,970 example is acting as an Internet server on the outside at the moment. 7 00:00:38,970 --> 00:00:49,610 Radu one is not able to ping router three out of four on the inside over here is also not able to ping 8 00:00:49,610 --> 00:00:52,230 rotisserie. 9 00:00:52,450 --> 00:00:53,620 The pings are failing 10 00:00:56,690 --> 00:01:02,180 and that's because there is no routing enabled on Rodda 3. 11 00:01:02,240 --> 00:01:05,130 It only has a directly connected network. 12 00:01:05,300 --> 00:01:09,200 It doesn't know how to send traffic back to those devices. 13 00:01:09,230 --> 00:01:18,800 We can see that by running debug debug IP ICMP debug IP packet I'll do a ping from a one to router three 14 00:01:18,850 --> 00:01:20,870 again. 15 00:01:20,990 --> 00:01:26,030 We can see messages here unrideable unrideable. 16 00:01:26,220 --> 00:01:30,370 So the traffic is getting from the internal hosts to the outside device. 17 00:01:30,370 --> 00:01:37,170 Robert 3 but rotisserie doesn't know how to route it back again because the ping is being received from 18 00:01:37,200 --> 00:01:44,070 10 1 1 1 so the local router is trying to send an echo reply back to that address but doesn't know how 19 00:01:44,070 --> 00:01:49,620 to get to that address because there is no rot in the writing table. 20 00:01:50,420 --> 00:01:58,150 To get router three to 10 one one one so neither Route 1 or rod of four are able to ping Rodda three. 21 00:01:58,210 --> 00:02:01,200 So let's enable that on rockety. 22 00:02:02,200 --> 00:02:08,000 So interface if 0 1 IP not outside. 23 00:02:08,180 --> 00:02:15,100 Now in this example we need to make an important distinction to the previous net examples in this example 24 00:02:15,110 --> 00:02:24,720 I am netting multiple devices to the same IP address on router 2 and that IP address is configured on. 25 00:02:24,730 --> 00:02:32,330 Ethan it is 0 1 so we are not allocating a missional IP addresses to Nat. 26 00:02:32,510 --> 00:02:37,090 This is probably the most common way of doing NAT in the real world. 27 00:02:37,340 --> 00:02:41,800 So Notice I'm using the term Nat and that's what most engineers will call it. 28 00:02:41,810 --> 00:02:48,830 But in actual fact it's Pat or port address translation or Knecht overloading because we taking multiple 29 00:02:49,010 --> 00:02:57,230 devices and overloading a single IP address to allow those devices to use that single IP address for 30 00:02:57,230 --> 00:02:59,420 access to the Internet. 31 00:02:59,420 --> 00:03:05,420 So what I've done thus far is enable Nat on the outside here and enable that on the inside of car. 32 00:03:05,720 --> 00:03:13,850 That's all I've done and I'm going to type IP Nat and I'm netting the inside devices. 33 00:03:13,850 --> 00:03:20,000 And in this case they source addresses based on an access list which I'll create in a moment access 34 00:03:20,060 --> 00:03:26,620 list one and I'm going to enact them to a physical interface first. 35 00:03:26,630 --> 00:03:31,440 Ethan it is 0 1 rather than allocating a separate IP address. 36 00:03:31,580 --> 00:03:39,230 And this is the important piece I'm going to overload this next entry to allow multiple devices to access 37 00:03:39,230 --> 00:03:42,410 the internet using that single address. 38 00:03:42,570 --> 00:03:51,320 I have to create to the access list one as referenced in my command access list one permit and who's 39 00:03:51,320 --> 00:03:53,630 going to be allowed to be nattered 40 00:03:57,160 --> 00:03:58,140 made a mistake. 41 00:03:58,200 --> 00:04:03,910 In this case it should be anyone in the 10 1 1 0 network. 42 00:04:03,930 --> 00:04:10,760 So anyone in this network will be nattered so show i.p that translation. 43 00:04:10,940 --> 00:04:13,310 No not translations at the moment. 44 00:04:14,130 --> 00:04:20,310 I'm going to enable Telenet on rotisserie 45 00:04:26,060 --> 00:04:28,210 and a of one I'll do a telnet to router three. 46 00:04:28,220 --> 00:04:36,530 But before I do that let's enable not debugging on router too so we can see the net debugging in real 47 00:04:36,530 --> 00:04:38,070 time. 48 00:04:38,070 --> 00:04:49,670 Telnet eight hundred one to two hit enter notice we can see the net translations taking place the source 49 00:04:49,670 --> 00:04:59,570 IP address 10 one on 1 is being netted 2 8 1 1 1 the IP address for traffic S. 2 8 1 1 2 the reply comes 50 00:04:59,570 --> 00:05:00,290 back. 51 00:05:00,590 --> 00:05:05,250 So Source 8 1 1 2 sending traffic 2 8 2 1 1 1. 52 00:05:05,390 --> 00:05:13,690 That is not to add 2 10 1 1 1 so I put my post-wedding of Cisco. 53 00:05:13,920 --> 00:05:19,140 We can see the translations taking place type a single character. 54 00:05:19,420 --> 00:05:25,140 There's the net translations show IP net translations. 55 00:05:25,230 --> 00:05:30,960 There's the dynamic net translation notice inside a local address 10 1 1 1. 56 00:05:31,000 --> 00:05:38,350 Using this ephemeral or random port number is being translated to 8 1 1 1 using the same port number 57 00:05:38,890 --> 00:05:42,940 going to 8 1 1 2 on port 23. 58 00:05:42,940 --> 00:05:50,390 So notice rotisseries not being translated but the entries for that address are shown in the table. 59 00:05:50,470 --> 00:05:55,510 Let's do a nother telnet so from Rotto 4 to 8 1 1 2 60 00:05:58,570 --> 00:06:09,360 and log in we can see 10 1 1 for this is not a full IP address is translated to 8 1 1 1 router TOS IP 61 00:06:09,360 --> 00:06:19,140 address for traffic going to 8 1 1 2 roaded 3s IP address show IP net translations we can see two dynamic 62 00:06:19,140 --> 00:06:25,680 and net translations one for 10 1 1 4 and 1 for 10 1 1 1. 63 00:06:25,680 --> 00:06:33,510 And this is how rodded to knows that the traffic is destined to win both Rodda 104 telnetting throughout 64 00:06:33,510 --> 00:06:38,360 history rotatory since traffic back to rodder too. 65 00:06:38,610 --> 00:06:47,810 But based on different port numbers and on router 3 Alceste type one character in noticed we could see 66 00:06:47,810 --> 00:06:49,100 sequence numbers here. 67 00:06:50,370 --> 00:07:00,270 Try type another character notice 2 8 8 3 2 2 8 8 3 3 3 4 3 5. 68 00:07:00,570 --> 00:07:03,620 And then for the return traffic we can see the sequence numbers as well. 69 00:07:03,690 --> 00:07:10,380 Show IP net translations there are translations once again what's important to remember is that when 70 00:07:10,380 --> 00:07:20,820 traffic is returned from rotatory to rodded to it's coming from the address 8 1 1 to port 23 going to 71 00:07:20,840 --> 00:07:22,840 this address 8 1 1 1. 72 00:07:23,100 --> 00:07:30,570 But using a port number so so rodded too is able to differentiate between the two sessions based on 73 00:07:30,570 --> 00:07:31,760 the port number. 74 00:07:31,830 --> 00:07:40,320 Hence the term port address translation when traffic arrives from rotisserie at rodded to with a destination 75 00:07:40,320 --> 00:07:43,600 port number of the US going to eight triple one. 76 00:07:43,680 --> 00:07:46,540 The traffic is going to be forwarded to Route 1. 77 00:07:46,800 --> 00:07:49,400 But when it arrives going to the same IP address. 78 00:07:49,410 --> 00:07:56,340 But this port number the traffic is forwarded to router for router to ensures that these port numbers 79 00:07:56,370 --> 00:07:58,780 are unique in the next table.