WEBVTT 00:01.730 --> 00:09.020 In this lecture, we'll see if they accept and drop targets again, it's more like a recap because we've 00:09.020 --> 00:11.950 already used them in so many examples. 00:12.620 --> 00:16.610 Both accept and drop are terminating targets. 00:17.980 --> 00:25.000 If a packet is matched against a ruler that has the accept or drop target, the packet is accepted or 00:25.000 --> 00:27.910 dropped and will not traverse the chain any more. 00:28.570 --> 00:30.460 Let me show you an example. 00:32.360 --> 00:40.670 I want to permit incoming pink pancakes only from a management station or from a single IP address before 00:40.670 --> 00:41.670 getting started. 00:41.690 --> 00:49.100 I want to explain to you what pink means in case you don't know, being is a utility comment available 00:49.100 --> 00:50.870 in any operating system. 00:51.080 --> 00:58.310 And it serves two primary purposes to check if the destination host is available and to measure the 00:58.310 --> 01:06.500 round trip time for messages sent from the originating host to a destination host that are echoed back 01:06.500 --> 01:07.250 to the source. 01:08.620 --> 01:17.260 According to Wikipedia, the name Ping comes from active sonar technology that sends a pulse of sound 01:17.260 --> 01:25.990 and listens for the echo to detect objects underwater ping or breaks by sending Internet control message 01:25.990 --> 01:33.380 protocol or ICMP echo request packets to the target host and waiting for ICMP reply packets. 01:33.910 --> 01:42.550 So allowing ping means, in fact allowing incoming ICMP echo request packets and outgoing ICMP echo 01:42.550 --> 01:43.540 reply packets. 01:44.690 --> 01:53.360 Lix seeks Help IAPT plus minus B ICMP, the protocol is ICMP minus minus help. 01:58.700 --> 02:07.910 We notice that we specify the type of ICMP packet using minus minus ICMP minus type, and these are 02:08.120 --> 02:10.430 all available ICMP types. 02:13.120 --> 02:17.440 Among them, we a reply and echo request. 02:19.850 --> 02:27.110 In this example, I'll write type table rules only for the input chain, so for incoming traffic, particular 02:27.150 --> 02:31.050 right IP table rules for the output chains as well. 02:31.580 --> 02:39.740 So the first rule will allow incoming ICMP packets of Type A. request if the source IP address is that 02:39.740 --> 02:41.140 of the management host. 02:42.350 --> 02:48.920 In this example, I'll consider the management host as being the Windows recording machine, which has 02:48.920 --> 02:50.000 the IP address. 02:53.460 --> 02:59.190 190 to 168 to zero that 112. 03:05.250 --> 03:16.080 IP table is minus A input, minus B, ICMP minus minus ICMP, minus type echo, minus request. 03:18.480 --> 03:19.500 Minus is. 03:22.960 --> 03:31.390 192 dot, 168 dot zero, that 112 minus G except. 03:35.100 --> 03:42.840 And the second rule that will drop all incoming ICMP request Bishkek's if the source address is another 03:42.840 --> 03:44.960 host, not the management station. 03:45.840 --> 03:57.750 So IP table is minus 18, both minus ICMP minus minus ICMP minus type Akko request minus J drop. 03:58.140 --> 04:02.330 In fact, it's the same rule without the minus option. 04:02.490 --> 04:07.050 So without the source IP address, let's test it. 04:08.060 --> 04:18.200 If al-Bakhit with the source IP address 192 dot 168, dot zero, dot 112 is coming, it will be accepted 04:18.200 --> 04:22.140 by the first one being a terminating target. 04:22.160 --> 04:28.910 The packet will not be evaluated by the second goal, which of course would drop it if it evaluated 04:28.910 --> 04:29.570 the packet. 04:30.730 --> 04:34.240 From the management station, I'm going to ping Linux on. 04:37.280 --> 04:43.160 And pink is working perfect, and I think the viral. 04:44.650 --> 04:47.520 And we see mixed paychecks by the first toll. 04:49.690 --> 04:56.690 Now, if an equal request packet is coming from another IP address, the first rule will not make. 04:57.040 --> 04:59.740 And the second one will drop the packet. 05:01.060 --> 05:02.980 Let's bring it from Lennox to. 05:08.410 --> 05:12.800 And we notice that Linux, too, is not receiving anything back. 05:13.300 --> 05:19.870 The second rule is dropping any Akko request packets coming from another source IP address. 05:23.570 --> 05:26.900 There are 37 dropped packets by the second.