1 1 00:00:00,240 --> 00:00:01,850 Access control lists. 2 2 00:00:01,850 --> 00:00:02,810 In this lesson, 3 3 00:00:02,810 --> 00:00:05,410 we're going to discuss how we can best secure our network 4 4 00:00:05,410 --> 00:00:08,010 using access control lists, firewall rule-sets, 5 5 00:00:08,010 --> 00:00:10,420 and how to configure role-based access. 6 6 00:00:10,420 --> 00:00:12,540 Now, an access control list, or ACL, 7 7 00:00:12,540 --> 00:00:13,990 is a list of permissions associated 8 8 00:00:13,990 --> 00:00:16,370 with a given system or network resource. 9 9 00:00:16,370 --> 00:00:19,210 An ACL can be applied to any packet filtering device, 10 10 00:00:19,210 --> 00:00:22,700 such as a router, a layer 3 switch, or a firewall. 11 11 00:00:22,700 --> 00:00:24,640 In an ACL, you're going to have a list of rules 12 12 00:00:24,640 --> 00:00:26,720 that are being applied based on an IP address, 13 13 00:00:26,720 --> 00:00:28,390 a port, or an application, 14 14 00:00:28,390 --> 00:00:29,510 depending on the type of device 15 15 00:00:29,510 --> 00:00:31,410 you're applying this ACL onto. 16 16 00:00:31,410 --> 00:00:32,910 Now, as the access control list 17 17 00:00:32,910 --> 00:00:34,460 is being processed by the device, 18 18 00:00:34,460 --> 00:00:36,150 it's going to start at the top of the list 19 19 00:00:36,150 --> 00:00:37,450 and work through each line 20 20 00:00:37,450 --> 00:00:39,350 until it reaches the end of that list. 21 21 00:00:39,350 --> 00:00:41,330 So we're going to work from top to bottom. 22 22 00:00:41,330 --> 00:00:43,030 Therefore, you always want to make sure 23 23 00:00:43,030 --> 00:00:45,080 your most specific rules are at the top, 24 24 00:00:45,080 --> 00:00:47,620 and your most generic rules are at the bottom. 25 25 00:00:47,620 --> 00:00:50,560 For example, let's pretend I had an access control list. 26 26 00:00:50,560 --> 00:00:52,610 as I'm working as a bouncer at a nightclub. 27 27 00:00:52,610 --> 00:00:53,670 Now, at the top of the list, 28 28 00:00:53,670 --> 00:00:55,320 I might have something very specific, 29 29 00:00:55,320 --> 00:00:57,050 like somebody's name, John Smith. 30 30 00:00:57,050 --> 00:00:59,400 He came in last week and he caused all sorts of trouble. 31 31 00:00:59,400 --> 00:01:01,730 So John Smith cannot come in the club. 32 32 00:01:01,730 --> 00:01:02,920 Now, as I move down the list, 33 33 00:01:02,920 --> 00:01:04,700 I may get to something more generic. 34 34 00:01:04,700 --> 00:01:06,270 So I might get to something that says anybody 35 35 00:01:06,270 --> 00:01:08,650 whose driver's license says they live in Montana, 36 36 00:01:08,650 --> 00:01:10,460 because I'm running a club in Florida. 37 37 00:01:10,460 --> 00:01:11,340 If that was the case, 38 38 00:01:11,340 --> 00:01:12,500 I might want to block that 39 39 00:01:12,500 --> 00:01:13,550 because maybe we had a lot of people 40 40 00:01:13,550 --> 00:01:15,360 coming with fake ideas from Montana, 41 41 00:01:15,360 --> 00:01:17,190 so we're not going to accept those anymore. 42 42 00:01:17,190 --> 00:01:18,730 Now, as we get to the end of that list, 43 43 00:01:18,730 --> 00:01:20,570 we might see something very generic. 44 44 00:01:20,570 --> 00:01:22,150 Something like no men allowed. 45 45 00:01:22,150 --> 00:01:23,780 Maybe this is a woman's only club. 46 46 00:01:23,780 --> 00:01:25,600 Now, this is a pretty generic rule, right? 47 47 00:01:25,600 --> 00:01:27,710 Because half of the people on the planet are men. 48 48 00:01:27,710 --> 00:01:30,020 So this is a very generic way of saying things. 49 49 00:01:30,020 --> 00:01:31,740 So as we go from the top to the bottom, 50 50 00:01:31,740 --> 00:01:33,920 we go from very specific, to more general, 51 51 00:01:33,920 --> 00:01:35,220 to the most general. 52 52 00:01:35,220 --> 00:01:37,280 Now, the same thing happens in our networks. 53 53 00:01:37,280 --> 00:01:39,410 If I'm going to create a rule to block SSH 54 54 00:01:39,410 --> 00:01:41,650 for a single computer based on its IP address, 55 55 00:01:41,650 --> 00:01:43,690 that's going to be towards the top of my list. 56 56 00:01:43,690 --> 00:01:46,830 If I want to block any IP address that's using port 110, 57 57 00:01:46,830 --> 00:01:48,210 that's going to be a bit more generic. 58 58 00:01:48,210 --> 00:01:49,720 So it'll be somewhere in the middle. 59 59 00:01:49,720 --> 00:01:52,790 Finally, if I want to block any IP going to any port, 60 60 00:01:52,790 --> 00:01:54,740 that is going to be something that is really generic, 61 61 00:01:54,740 --> 00:01:56,640 and it should be at the end of my list. 62 62 00:01:56,640 --> 00:01:58,580 So let's talk about some things 63 63 00:01:58,580 --> 00:02:00,870 that we may want to block using our ACLs 64 64 00:02:00,870 --> 00:02:03,290 in order to help secure our networks better. 65 65 00:02:03,290 --> 00:02:04,780 Now, first we want to make sure 66 66 00:02:04,780 --> 00:02:06,410 we're blocking incoming requests 67 67 00:02:06,410 --> 00:02:08,580 from internal or private loop back addresses, 68 68 00:02:08,580 --> 00:02:12,100 or multicast IP ranges, or experimental ranges, 69 69 00:02:12,100 --> 00:02:14,190 if we have something that's coming from outside 70 70 00:02:14,190 --> 00:02:16,070 of the network going into our network. 71 71 00:02:16,070 --> 00:02:17,670 So if you have something that says 72 72 00:02:17,670 --> 00:02:21,120 it's coming from 192.168 dot something, dot something, 73 73 00:02:21,120 --> 00:02:23,040 and it's coming from the internet interface, 74 74 00:02:23,040 --> 00:02:24,960 well, that's a non-routable IP, 75 75 00:02:24,960 --> 00:02:26,260 and it shouldn't be coming from there. 76 76 00:02:26,260 --> 00:02:27,930 So you should be blocking that. 77 77 00:02:27,930 --> 00:02:29,030 That should never be allowed 78 78 00:02:29,030 --> 00:02:30,920 to come into your network from the internet, 79 79 00:02:30,920 --> 00:02:33,950 because usually it's an attacker trying to spoof their IP. 80 80 00:02:33,950 --> 00:02:34,783 Similarly, 81 81 00:02:34,783 --> 00:02:36,460 if you start seeing source IP addresses 82 82 00:02:36,460 --> 00:02:38,010 coming from areas that are reserved for things 83 83 00:02:38,010 --> 00:02:40,600 like loop back or experimental IP ranges, 84 84 00:02:40,600 --> 00:02:43,630 those things should also be blocked immediately. 85 85 00:02:43,630 --> 00:02:44,463 Second, 86 86 00:02:44,463 --> 00:02:45,900 you want to block incoming requests 87 87 00:02:45,900 --> 00:02:48,500 from protocols that should only be used locally. 88 88 00:02:48,500 --> 00:02:49,360 For example, 89 89 00:02:49,360 --> 00:02:53,300 if you have ICMP, DHCP, OSPF, SMB, 90 90 00:02:53,300 --> 00:02:54,720 and other things like that, 91 91 00:02:54,720 --> 00:02:56,820 you want to block those at the firewall 92 92 00:02:56,820 --> 00:02:58,720 as things try to enter your network. 93 93 00:02:58,720 --> 00:03:00,620 Now, if you have something like Windows file sharing, 94 94 00:03:00,620 --> 00:03:02,700 for instance, which operates over SMB, 95 95 00:03:02,700 --> 00:03:04,720 that should not be happening over the internet. 96 96 00:03:04,720 --> 00:03:05,810 That is something that should happen 97 97 00:03:05,810 --> 00:03:07,730 inside the local network only. 98 98 00:03:07,730 --> 00:03:08,563 So again, 99 99 00:03:08,563 --> 00:03:10,350 you should be blocking that at the firewall 100 100 00:03:10,350 --> 00:03:11,930 at the border of your network. 101 101 00:03:11,930 --> 00:03:14,050 If somebody has a VPN and they're working from home, 102 102 00:03:14,050 --> 00:03:16,080 they'll be able to tunnel through your firewall, 103 103 00:03:16,080 --> 00:03:17,400 access the local network, 104 104 00:03:17,400 --> 00:03:19,430 and then use SMB that way. 105 105 00:03:19,430 --> 00:03:21,960 But they shouldn't be using it straight from their home 106 106 00:03:21,960 --> 00:03:23,570 over the internet to your network. 107 107 00:03:23,570 --> 00:03:25,610 They should only do it through a VPN. 108 108 00:03:25,610 --> 00:03:27,390 Now, the third thing you want to consider 109 109 00:03:27,390 --> 00:03:29,840 is how you want to configure IPv6. 110 110 00:03:29,840 --> 00:03:30,910 Now, I recommend you either 111 111 00:03:30,910 --> 00:03:34,300 configure IPv6 to block all IPv6 traffic, 112 112 00:03:34,300 --> 00:03:37,410 or you allow it only to authorize hosts and ports 113 113 00:03:37,410 --> 00:03:39,660 if you're using IPv6 in your network. 114 114 00:03:39,660 --> 00:03:41,860 The reason for this is because a lot of hosts 115 115 00:03:41,860 --> 00:03:44,690 will run dual stack TCP/IP implementations 116 116 00:03:44,690 --> 00:03:47,180 with IPv6 enabled by default. 117 117 00:03:47,180 --> 00:03:48,580 And if you're not aware of that, 118 118 00:03:48,580 --> 00:03:50,740 you're going to be having a lot of these things open, 119 119 00:03:50,740 --> 00:03:51,620 and you're letting people have 120 120 00:03:51,620 --> 00:03:53,680 unfettered access to your network. 121 121 00:03:53,680 --> 00:03:56,720 A lot of organizations are still running IPv4 only, 122 122 00:03:56,720 --> 00:03:57,690 and if they're doing that, 123 123 00:03:57,690 --> 00:04:00,590 they definitely need to turn off IPv6 on those hosts, 124 124 00:04:00,590 --> 00:04:03,120 and they need to configure their firewall to block it. 125 125 00:04:03,120 --> 00:04:04,000 If you don't do this, 126 126 00:04:04,000 --> 00:04:05,560 you could have a misconfiguration 127 127 00:04:05,560 --> 00:04:07,720 that could allow adversaries unfiltered access 128 128 00:04:07,720 --> 00:04:11,400 into your networks by using that IPv6 IP address area, 129 129 00:04:11,400 --> 00:04:12,810 because a lot of administrators 130 130 00:04:12,810 --> 00:04:15,700 simply haven't locked down IPv6 well enough yet. 131 131 00:04:15,700 --> 00:04:17,360 So keep this in mind as you're doing 132 132 00:04:17,360 --> 00:04:19,070 your configurations on your firewalls 133 133 00:04:19,070 --> 00:04:20,800 and your access control lists. 134 134 00:04:20,800 --> 00:04:21,633 All right. 135 135 00:04:21,633 --> 00:04:23,530 Now that we have some basic rules out of the way, 136 136 00:04:23,530 --> 00:04:25,860 let's take a look at an access control list, 137 137 00:04:25,860 --> 00:04:27,360 and walk through it together. 138 138 00:04:27,360 --> 00:04:29,800 Now, this one is an example from a Cisco firewall, 139 139 00:04:29,800 --> 00:04:31,510 but that really doesn't matter for this exam, 140 140 00:04:31,510 --> 00:04:33,640 because when we're talking about CompTIA exams, 141 141 00:04:33,640 --> 00:04:35,230 they are device agnostic. 142 142 00:04:35,230 --> 00:04:36,420 This could've come from a router. 143 143 00:04:36,420 --> 00:04:37,670 It could've come from a firewall. 144 144 00:04:37,670 --> 00:04:39,530 It could've come from Cisco, or Juniper, or Brocade. 145 145 00:04:39,530 --> 00:04:40,910 It really doesn't matter. 146 146 00:04:40,910 --> 00:04:42,640 The point is I want you be able to read 147 147 00:04:42,640 --> 00:04:45,180 a basic firewall like this and understand it, 148 148 00:04:45,180 --> 00:04:47,830 because that will make sure you're doing well on the exam. 149 149 00:04:47,830 --> 00:04:50,090 So let's start out with the first line. 150 150 00:04:50,090 --> 00:04:53,160 ip access-list extended From-DMZ. 151 151 00:04:53,160 --> 00:04:55,220 This just says that this is an access list. 152 152 00:04:55,220 --> 00:04:58,410 And in this case, I'm using it for my DMZ. 153 153 00:04:58,410 --> 00:05:00,840 The second line is a comment or remark line. 154 154 00:05:00,840 --> 00:05:03,200 This is going to tell you what this section is about. 155 155 00:05:03,200 --> 00:05:04,420 Basically, it's saying that we're 156 156 00:05:04,420 --> 00:05:06,720 going to have responses to HTTP requests, 157 157 00:05:06,720 --> 00:05:09,370 and that we're going to get a bunch of permit statements here. 158 158 00:05:09,370 --> 00:05:11,280 Now, as we go through these permit statements, 159 159 00:05:11,280 --> 00:05:12,850 we're going to look at them one at a time, 160 160 00:05:12,850 --> 00:05:13,900 and it's going to tell us which things 161 161 00:05:13,900 --> 00:05:15,670 are being permitted or denied. 162 162 00:05:15,670 --> 00:05:17,030 Now, when we see the word permit, 163 163 00:05:17,030 --> 00:05:18,650 that means we're going to allow something, 164 164 00:05:18,650 --> 00:05:19,483 and in this case, 165 165 00:05:19,483 --> 00:05:21,390 we're going to allow TCP traffic. 166 166 00:05:21,390 --> 00:05:23,220 So we have permit tcp, 167 167 00:05:23,220 --> 00:05:24,830 and then we have the IP address 168 168 00:05:24,830 --> 00:05:26,420 that's going to be associated with it. 169 169 00:05:26,420 --> 00:05:28,750 In this case, we're going to permit TCP traffic 170 170 00:05:28,750 --> 00:05:32,450 coming from the IP address 10.0.2.0. 171 171 00:05:32,450 --> 00:05:35,040 The next thing we have is going to be our wildcard mask, 172 172 00:05:35,040 --> 00:05:36,800 which acts like a subnet mask. 173 173 00:05:36,800 --> 00:05:38,200 Now, this looks a little funny 174 174 00:05:38,200 --> 00:05:39,470 because it's a wildcard mask 175 175 00:05:39,470 --> 00:05:41,290 and it's technically a reverse wild card, 176 176 00:05:41,290 --> 00:05:43,443 and it's written as 0.0.0.255. 177 177 00:05:44,710 --> 00:05:47,310 So if you want to read this as a subnet mask, 178 178 00:05:47,310 --> 00:05:48,680 you actually have to convert it. 179 179 00:05:48,680 --> 00:05:52,870 And essentially you're going to make it 255.255.255.0. 180 180 00:05:52,870 --> 00:05:54,270 This is a Cisco thing. 181 181 00:05:54,270 --> 00:05:56,840 When you see the zero in the reverse wildcard, 182 182 00:05:56,840 --> 00:05:58,490 treat that as a 255. 183 183 00:05:58,490 --> 00:06:00,950 If you see a 255, treat it as a zero. 184 184 00:06:00,950 --> 00:06:02,610 Don't let this get you confused. 185 185 00:06:02,610 --> 00:06:04,410 Essentially what we're saying here 186 186 00:06:04,410 --> 00:06:06,390 is that we're permitting TCP traffic 187 187 00:06:06,390 --> 00:06:10,450 from any IP that is 10.0.2 dot something, 188 188 00:06:10,450 --> 00:06:13,680 because this is the 10.0.2.0 network, 189 189 00:06:13,680 --> 00:06:17,180 and it has 256 possible IPs that we're going to use here. 190 190 00:06:17,180 --> 00:06:20,760 Anything in this IP range will be permitted under this rule. 191 191 00:06:20,760 --> 00:06:24,170 The next part you see is eq, which stands for equal. 192 192 00:06:24,170 --> 00:06:27,560 So the IP address has whatever is beyond this equal sign, 193 193 00:06:27,560 --> 00:06:29,150 and that's going to be allowed. 194 194 00:06:29,150 --> 00:06:31,187 In this case, we're equaling www. 195 195 00:06:32,100 --> 00:06:33,390 Now, what does that mean? 196 196 00:06:33,390 --> 00:06:34,630 It means port 80. 197 197 00:06:34,630 --> 00:06:38,430 Www is Cisco's way of saying this is web traffic. 198 198 00:06:38,430 --> 00:06:40,400 Somebody can make a request over port 80, 199 199 00:06:40,400 --> 00:06:42,060 and we're going to allow it. 200 200 00:06:42,060 --> 00:06:44,070 Next we have the part that says any, 201 201 00:06:44,070 --> 00:06:45,580 and this says that we're going to be going 202 202 00:06:45,580 --> 00:06:48,480 to any IP address as our destination. 203 203 00:06:48,480 --> 00:06:51,310 So we can go to any web server in the world over port 80, 204 204 00:06:51,310 --> 00:06:52,710 and we're going to allow it. 205 205 00:06:52,710 --> 00:06:54,950 This will allow us to make an established connection there, 206 206 00:06:54,950 --> 00:06:56,270 and then start traffic. 207 207 00:06:56,270 --> 00:06:58,060 So any time we want to make an established connection 208 208 00:06:58,060 --> 00:07:02,040 from 10.0.2 dot something to some website over port 80, 209 209 00:07:02,040 --> 00:07:04,250 we're going to allow that using TCP. 210 210 00:07:04,250 --> 00:07:05,910 Essentially that's what we're saying. 211 211 00:07:05,910 --> 00:07:07,880 People can go out and access a website 212 212 00:07:07,880 --> 00:07:10,010 from our DMZ out to the internet, 213 213 00:07:10,010 --> 00:07:12,670 and this is all we're saying with this particular line. 214 214 00:07:12,670 --> 00:07:13,700 Now, as you go through 215 215 00:07:13,700 --> 00:07:16,250 and you read all these different lines in the ACL, 216 216 00:07:16,250 --> 00:07:17,260 you can start figuring out 217 217 00:07:17,260 --> 00:07:19,290 what is permitted and what is denied. 218 218 00:07:19,290 --> 00:07:21,690 In this case, everything shown here is permitted 219 219 00:07:21,690 --> 00:07:24,240 because we're doing explicit allow permissions. 220 220 00:07:24,240 --> 00:07:25,710 What we're saying is yes, 221 221 00:07:25,710 --> 00:07:27,330 all of these things are allowed. 222 222 00:07:27,330 --> 00:07:29,770 Permit them from this IP and this port 223 223 00:07:29,770 --> 00:07:31,970 going to that IP and that port. 224 224 00:07:31,970 --> 00:07:34,360 But as we go through to the bottom of this list, 225 225 00:07:34,360 --> 00:07:36,700 you'll see one statement that looks a little different. 226 226 00:07:36,700 --> 00:07:39,350 It says deny IP any any. 227 227 00:07:39,350 --> 00:07:42,160 Now, this is what's known as an implicit deny. 228 228 00:07:42,160 --> 00:07:43,290 This says that anything 229 229 00:07:43,290 --> 00:07:46,190 that is not already allowed above in my ACO rule-set 230 230 00:07:46,190 --> 00:07:48,480 is something we're just going to deny by default. 231 231 00:07:48,480 --> 00:07:50,140 So if we get down this list 232 232 00:07:50,140 --> 00:07:55,110 and you see things like www, 443, echo reply, domain, 233 233 00:07:55,110 --> 00:07:56,940 these are all things that we're allowing. 234 234 00:07:56,940 --> 00:07:59,010 And then when I talk about domain here, 235 235 00:07:59,010 --> 00:08:01,310 I'm not really talking about domain in general, 236 236 00:08:01,310 --> 00:08:03,390 but we're talking about DNS as a service, 237 237 00:08:03,390 --> 00:08:06,070 because this is the way Cisco talks about DNS services. 238 238 00:08:06,070 --> 00:08:07,340 When they say domain, 239 239 00:08:07,340 --> 00:08:10,450 we are really talking about equaling port 53. 240 240 00:08:10,450 --> 00:08:11,820 So in this case, 241 241 00:08:11,820 --> 00:08:13,260 everything you see listed here 242 242 00:08:13,260 --> 00:08:15,070 is all these different permit statements 243 243 00:08:15,070 --> 00:08:18,270 that are going to allow traffic from our DMZ to the internet. 244 244 00:08:18,270 --> 00:08:19,180 The DMZ can go out 245 245 00:08:19,180 --> 00:08:22,070 and get web traffic over port 80 or port 443. 246 246 00:08:22,070 --> 00:08:24,870 It can reply to echo requests, which is ICMP. 247 247 00:08:24,870 --> 00:08:28,970 It can use port 53, which is domain, over UDP and TCP. 248 248 00:08:28,970 --> 00:08:29,803 These are all things 249 249 00:08:29,803 --> 00:08:32,820 that we're going to be allowed to do from this DMZ. 250 250 00:08:32,820 --> 00:08:35,050 But when I get down to that last statement, 251 251 00:08:35,050 --> 00:08:36,880 if any of those things didn't happen, 252 252 00:08:36,880 --> 00:08:38,150 we are going to deny it. 253 253 00:08:38,150 --> 00:08:39,090 So for example, 254 254 00:08:39,090 --> 00:08:42,600 if somebody tries to go to port 21 and access FTP, 255 255 00:08:42,600 --> 00:08:45,600 we're going to reach that deny IP any any statement, 256 256 00:08:45,600 --> 00:08:47,220 and it's going to be blocked. 257 257 00:08:47,220 --> 00:08:48,480 This is because that statement 258 258 00:08:48,480 --> 00:08:52,570 will deny any IP going from any IP to any IP. 259 259 00:08:52,570 --> 00:08:55,970 Essentially, this ACL is configured as a white list. 260 260 00:08:55,970 --> 00:08:57,420 It's only going to allow things 261 261 00:08:57,420 --> 00:09:00,430 that are being permitted explicitly listed in this list, 262 262 00:09:00,430 --> 00:09:02,520 and everything else is going to be blocked. 263 263 00:09:02,520 --> 00:09:04,750 This is a good way of doing your security. 264 264 00:09:04,750 --> 00:09:07,470 Now, we just mentioned the concept of explicit allow, 265 265 00:09:07,470 --> 00:09:09,270 but we can also have firewall rules 266 266 00:09:09,270 --> 00:09:12,400 that will use explicit deny or implicit deny. 267 267 00:09:12,400 --> 00:09:14,620 Now, when you have an explicit deny statement, 268 268 00:09:14,620 --> 00:09:15,860 you're creating a rule to block 269 269 00:09:15,860 --> 00:09:17,490 some kind of matching traffic. 270 270 00:09:17,490 --> 00:09:18,900 In this example I showed you, 271 271 00:09:18,900 --> 00:09:21,030 we didn't have any explicit deny statements, 272 272 00:09:21,030 --> 00:09:22,470 but they would look exactly the same 273 273 00:09:22,470 --> 00:09:23,730 as our permit statements, 274 274 00:09:23,730 --> 00:09:26,160 except we would change the word permit to deny. 275 275 00:09:26,160 --> 00:09:27,450 Now, this allows us to go 276 276 00:09:27,450 --> 00:09:30,170 from an explicit allow to an explicit deny. 277 277 00:09:30,170 --> 00:09:32,360 So let's say I wanted to block traffic 278 278 00:09:32,360 --> 00:09:35,350 going to the IP address of 8.8.8.8. 279 279 00:09:35,350 --> 00:09:36,530 I could create a rule that says 280 280 00:09:36,530 --> 00:09:41,530 deny IP 8.8.8.8 0.0.0.0 any any. 281 281 00:09:42,100 --> 00:09:43,460 And it's going to block all ports 282 282 00:09:43,460 --> 00:09:47,720 and all protocols going to the IP address of 8.8.8.8. 283 283 00:09:47,720 --> 00:09:51,760 Now, notice my reverse card mask there was 0.0.0.0, 284 284 00:09:51,760 --> 00:09:54,660 which tells me I only want to match this IP. 285 285 00:09:54,660 --> 00:09:58,640 Not a whole network, just the IP of 8.8.8.8. 286 286 00:09:58,640 --> 00:10:01,490 On the other hand, I can also use an implicit deny, 287 287 00:10:01,490 --> 00:10:04,980 which blocks traffic to anything not explicitly specified. 288 288 00:10:04,980 --> 00:10:06,730 In the example ACL I showed you, 289 289 00:10:06,730 --> 00:10:09,740 that last statement had that implicit deny. 290 290 00:10:09,740 --> 00:10:12,630 Basically anything not already explicitly allowed 291 291 00:10:12,630 --> 00:10:14,890 by an allow statement is going to get blocked 292 292 00:10:14,890 --> 00:10:17,740 because we had that deny IP any any statement 293 293 00:10:17,740 --> 00:10:20,570 as the last statement at the end of our ACL. 294 294 00:10:20,570 --> 00:10:23,540 Finally, we need to talk about role-based access. 295 295 00:10:23,540 --> 00:10:25,950 Role-based access allows you to define the privileges 296 296 00:10:25,950 --> 00:10:28,210 and responsibilities of administrative users 297 297 00:10:28,210 --> 00:10:30,740 who control your firewalls and their ACL's. 298 298 00:10:30,740 --> 00:10:31,940 With role-based access, 299 299 00:10:31,940 --> 00:10:33,750 we put different accounts into groups 300 300 00:10:33,750 --> 00:10:35,820 based on their roles or job functions. 301 301 00:10:35,820 --> 00:10:37,380 Then based on those roles, 302 302 00:10:37,380 --> 00:10:38,450 we're going to assign permissions 303 303 00:10:38,450 --> 00:10:41,160 to which devices they can configure and modify. 304 304 00:10:41,160 --> 00:10:42,240 So for example, 305 305 00:10:42,240 --> 00:10:43,520 if I'm responsible for updating 306 306 00:10:43,520 --> 00:10:44,870 and configuring the border gateway 307 307 00:10:44,870 --> 00:10:46,270 or firewall for the network, 308 308 00:10:46,270 --> 00:10:48,560 I would get access to add things to the ACL 309 309 00:10:48,560 --> 00:10:50,500 that would open or restrict communication 310 310 00:10:50,500 --> 00:10:52,730 between the internet and the internal network. 311 311 00:10:52,730 --> 00:10:53,580 On the other hand, 312 312 00:10:53,580 --> 00:10:55,010 if I'm just a switch technician 313 313 00:10:55,010 --> 00:10:57,150 who's responsible for adding and removing users 314 314 00:10:57,150 --> 00:10:58,680 when they're assigned to a new office, 315 315 00:10:58,680 --> 00:11:00,080 my role would not allow me 316 316 00:11:00,080 --> 00:11:02,880 to modify a layer 3 switch's ACLs, 317 317 00:11:02,880 --> 00:11:04,420 but instead would only allow me 318 318 00:11:04,420 --> 00:11:06,440 to shut down or reenable switchports 319 319 00:11:06,440 --> 00:11:07,943 and configure port security.