1 00:00:09,075 --> 00:00:12,400 - In this video I'd like to talk about Voice VLANs. 2 00:00:12,400 --> 00:00:15,444 So, up until now as you're watching this video, 3 00:00:15,444 --> 00:00:17,520 hopefully you've already learned about the concept of just 4 00:00:17,520 --> 00:00:20,398 regular VLANs and you've learned about the concept of 5 00:00:20,398 --> 00:00:23,572 what's called an access port on a switch. 6 00:00:23,572 --> 00:00:27,511 So on a Cisco switch when you type switchport mode access 7 00:00:27,511 --> 00:00:30,240 on an interface, normally that tells the interface 8 00:00:30,240 --> 00:00:32,839 you are in one broadcast domain. 9 00:00:32,839 --> 00:00:34,436 It doesn't know what broadcast domain. 10 00:00:34,436 --> 00:00:37,364 It will assume VLAN1 by default and then you have to 11 00:00:37,364 --> 00:00:39,544 pair that up with the additional command of 12 00:00:39,544 --> 00:00:43,284 switchport access VLAN and then some number, 13 00:00:43,284 --> 00:00:46,937 like switchport access VLAN7, or VLAN6, 14 00:00:46,937 --> 00:00:50,422 which says that any frame that comes in this interface 15 00:00:50,422 --> 00:00:53,776 that's an untagged Ethernet frame will be assigned to that 16 00:00:53,776 --> 00:00:56,693 broadcast domain of VLAN7 or VLAN6, 17 00:00:57,682 --> 00:00:59,321 whatever you've configured. 18 00:00:59,321 --> 00:01:00,925 Then if the other thing you've learned 19 00:01:00,925 --> 00:01:03,898 is this concept of trunks, VLAN trunks, 20 00:01:03,898 --> 00:01:06,870 which can be formed either with switchport mode trunk 21 00:01:06,870 --> 00:01:10,771 or switchport mode dynamic and then dynamic auto 22 00:01:10,771 --> 00:01:13,809 or dynamic desirable, which now means all of the 23 00:01:13,809 --> 00:01:16,853 broadcast domains that you know about, Mister Switch, 24 00:01:16,853 --> 00:01:18,686 VLAN7, VLAN9, VLAN200, 25 00:01:19,655 --> 00:01:23,316 all of them are permissible on this one interface. 26 00:01:23,316 --> 00:01:25,660 The native VLAN will be untagged. 27 00:01:25,660 --> 00:01:28,964 All other Ethernet frames will an 802.1q tag 28 00:01:28,964 --> 00:01:32,425 applied to indicate what VLAN they belong to. 29 00:01:32,425 --> 00:01:35,524 Voice VLAN's is something like right in the middle 30 00:01:35,524 --> 00:01:39,309 so let's talk about what voice VLANS do. 31 00:01:39,309 --> 00:01:41,681 So first of all, what problem is solved by voice VLANs? 32 00:01:41,681 --> 00:01:43,889 Why did they create them? 33 00:01:43,889 --> 00:01:45,960 So here we have your typical situation 34 00:01:45,960 --> 00:01:47,825 where you have an IP phone, 35 00:01:47,825 --> 00:01:50,281 and I'm just going to reference a Cisco IP phone, 36 00:01:50,281 --> 00:01:53,858 connected to your switchport and then you also have, 37 00:01:53,858 --> 00:01:56,625 connected to that phone, some sort of data device, 38 00:01:56,625 --> 00:01:58,292 like a PC or laptop. 39 00:01:59,664 --> 00:02:03,759 And our challenge here is that this switchport right here 40 00:02:03,759 --> 00:02:06,565 is going to be receiving frames that were sourced 41 00:02:06,565 --> 00:02:09,549 by the phone which is carrying your voice traffic. 42 00:02:09,549 --> 00:02:11,745 It's also going to be receiving ingress frames 43 00:02:11,745 --> 00:02:15,126 that were sourced by the laptop, which is your data traffic, 44 00:02:15,126 --> 00:02:19,425 and ideally we want some way for that switch to be able to 45 00:02:19,425 --> 00:02:23,592 tell the difference between frames that were sourced 46 00:02:24,545 --> 00:02:27,962 from the PC as data frames, versus frames 47 00:02:29,272 --> 00:02:33,451 that were sourced from the phone as voice frames. 48 00:02:33,451 --> 00:02:36,056 And the reason we want to be able to differentiate them 49 00:02:36,056 --> 00:02:39,045 is maybe to apply different policy levels to them. 50 00:02:39,045 --> 00:02:41,273 We're talking about quality of service now. 51 00:02:41,273 --> 00:02:45,868 So when the frames come in we want to be able to treat 52 00:02:45,868 --> 00:02:48,688 the voice frames with a higher level of priority, 53 00:02:48,688 --> 00:02:52,380 a higher level of service than we treat the data frames. 54 00:02:52,380 --> 00:02:54,780 So we need to be able to tell the difference between them 55 00:02:54,780 --> 00:02:58,697 and here is where a Voice VLAN comes into play. 56 00:02:59,773 --> 00:03:02,040 So with Voice VLANs it gives us the ability 57 00:03:02,040 --> 00:03:04,810 to basically have two broadcast domains 58 00:03:04,810 --> 00:03:07,350 assigned to this interface on the switch. 59 00:03:07,350 --> 00:03:09,895 We have one broadcast domain which will be for our 60 00:03:09,895 --> 00:03:14,782 access VLAN, which is our data, our untagged Ethernet frames 61 00:03:14,782 --> 00:03:17,935 from the laptop and then we'll have another VLAN 62 00:03:17,935 --> 00:03:22,232 also on this interface which will allow 802.1q tags. 63 00:03:22,232 --> 00:03:24,292 And that will presumably be the traffic 64 00:03:24,292 --> 00:03:29,210 that's carrying our voice inside of the Ethernet frames. 65 00:03:29,210 --> 00:03:30,897 So you can sort of think of this as like 66 00:03:30,897 --> 00:03:35,064 a little mini 802.1q trunk but unlike a normal 802.1q trunk 67 00:03:36,727 --> 00:03:40,004 which could be carrying potentially hundreds of VLANs 68 00:03:40,004 --> 00:03:43,833 with hundreds of different 802.1q tag values, 69 00:03:43,833 --> 00:03:48,028 here we've only got two broadcast domains, not all of the 70 00:03:48,028 --> 00:03:52,379 broadcast domains that this switch might be aware of. 71 00:03:52,379 --> 00:03:55,632 And the way this works here is that inside the IP phone 72 00:03:55,632 --> 00:03:58,310 itself there's actually like a little mini switch. 73 00:03:58,310 --> 00:04:01,970 They say it's like a three port switch so inside the IP 74 00:04:01,970 --> 00:04:05,783 phone you have it's switch, you have one port which is the 75 00:04:05,783 --> 00:04:09,913 data port, and usually if you turn the IP phone around 76 00:04:09,913 --> 00:04:13,421 you'll see on the back of it a little RJ45 that'll say 77 00:04:13,421 --> 00:04:16,838 to PC, right, so this will say here to PC 78 00:04:18,190 --> 00:04:20,292 typically or something like that. 79 00:04:20,292 --> 00:04:22,849 And then you'll see another RJ45 port 80 00:04:22,849 --> 00:04:26,099 which will say something like to switch 81 00:04:31,227 --> 00:04:32,459 and then what you don't realize is 82 00:04:32,459 --> 00:04:35,642 there's another sort of third internal switchport 83 00:04:35,642 --> 00:04:37,575 which goes to the actual CPU, 84 00:04:37,575 --> 00:04:40,926 the Central Processing Unit of the phone itself. 85 00:04:40,926 --> 00:04:44,078 So that's why we say there's like a three port mini switch 86 00:04:44,078 --> 00:04:46,632 inside the phone itself. 87 00:04:46,632 --> 00:04:50,666 And the Voice VLAN feature on the Cisco switch allows us 88 00:04:50,666 --> 00:04:54,833 to program that little mini switch inside the phone. 89 00:04:58,331 --> 00:05:00,631 So it's useful for isolating user data 90 00:05:00,631 --> 00:05:03,964 and voice traffic in the same interface. 91 00:05:05,865 --> 00:05:07,958 OK, so like I said, voice VLANs implies 92 00:05:07,958 --> 00:05:12,385 that there are two VLANs operating on one switchport. 93 00:05:12,385 --> 00:05:14,743 Your access VLAN, which is what your 94 00:05:14,743 --> 00:05:18,293 data traffic will be using, and your voice VLAN 95 00:05:18,293 --> 00:05:21,543 and both must be explicitly configured. 96 00:05:23,024 --> 00:05:24,984 Now the access VLAN, that's configured 97 00:05:24,984 --> 00:05:27,046 the same old way you've always done it. 98 00:05:27,046 --> 00:05:31,213 Switchport mode access, switchport access VLAN, whatever. 99 00:05:32,427 --> 00:05:34,168 So it's no different, and notice, 100 00:05:34,168 --> 00:05:37,668 your mode is still switchport mode access. 101 00:05:38,976 --> 00:05:39,857 The only thing that's different is 102 00:05:39,857 --> 00:05:41,321 we're now going to have a new command 103 00:05:41,321 --> 00:05:43,917 that you haven't seen before to define 104 00:05:43,917 --> 00:05:46,102 what the Voice VLAN is. 105 00:05:46,102 --> 00:05:50,023 Now that helps the switch, the Cisco switch, your 3560, 106 00:05:50,023 --> 00:05:52,801 your 6500, that helps that switch to know, 107 00:05:52,801 --> 00:05:56,208 oh, OK, when I see an ingress frame coming in that's got 108 00:05:56,208 --> 00:05:59,958 an 802.1q tag that says this value may be 90, 109 00:06:01,383 --> 00:06:03,743 I know that's my voice VLAN. 110 00:06:03,743 --> 00:06:04,872 That's a separate VLAN. 111 00:06:04,872 --> 00:06:06,913 I need to do something different with that, 112 00:06:06,913 --> 00:06:10,618 but how do we tell the phone, how do we tell the IP phone, 113 00:06:10,618 --> 00:06:14,200 hey, when you take that voice traffic 114 00:06:14,200 --> 00:06:17,702 and you encapsulate it inside Ethernet frames I want you to 115 00:06:17,702 --> 00:06:21,632 tag that with an 802.1q tag and here's the value. 116 00:06:21,632 --> 00:06:25,321 I want you to put the VLAN90 or VLAN7 in there. 117 00:06:25,321 --> 00:06:28,269 So how do we get that information to the phone? 118 00:06:28,269 --> 00:06:30,277 Well you can see here there's one of two ways. 119 00:06:30,277 --> 00:06:31,921 If it's a Cisco IP phone 120 00:06:31,921 --> 00:06:35,844 we can actually utilize the Cisco Discovery Protocol. 121 00:06:35,844 --> 00:06:40,372 CDP can push down to the phone how it should be reacting 122 00:06:40,372 --> 00:06:42,198 to VLANs and how it should be tagging 123 00:06:42,198 --> 00:06:45,475 or potentially not tagging stuff. 124 00:06:45,475 --> 00:06:47,981 If it's not a Cisco IP phone, well then there is a 125 00:06:47,981 --> 00:06:52,688 specific option, option 156, that you can use in DHCP. 126 00:06:52,688 --> 00:06:55,784 So the DHCP server itself can be preconfigured 127 00:06:55,784 --> 00:06:59,617 to push that information down to the IP phone. 128 00:07:00,737 --> 00:07:03,997 So here's our command: switchport voice vlan, 129 00:07:03,997 --> 00:07:06,314 and you can see you've got four options here. 130 00:07:06,314 --> 00:07:08,331 You can actually type a VLAN ID and this is what 131 00:07:08,331 --> 00:07:12,498 most people do, switchport voice VLAN7, or voice VLAN90. 132 00:07:14,089 --> 00:07:16,896 Most of the time that's what people do 133 00:07:16,896 --> 00:07:18,679 but on this slide I'm going to show you what all these 134 00:07:18,679 --> 00:07:22,528 various options do so you can sort of get an idea as to how 135 00:07:22,528 --> 00:07:25,027 the Ethernet frames are manipulated and what's 136 00:07:25,027 --> 00:07:28,074 actually being instructed to the IP phone 137 00:07:28,074 --> 00:07:31,085 based on these various options here. 138 00:07:31,085 --> 00:07:34,603 So let's start where you say switchport voice vlan and then 139 00:07:34,603 --> 00:07:38,857 you say, like, the number seven, as an example. 140 00:07:38,857 --> 00:07:42,357 So let us put the number seven right here. 141 00:07:45,702 --> 00:07:47,559 OK, so what that would mean, 142 00:07:47,559 --> 00:07:51,443 I'm going to go ahead and expand this a little bit. 143 00:07:51,443 --> 00:07:55,737 That means that when the IP phone sends it's voice traffic 144 00:07:55,737 --> 00:07:58,079 inside of an Ethernet frame 145 00:07:58,079 --> 00:08:00,246 it would put an 802.1q tag 146 00:08:03,484 --> 00:08:06,979 that would say the VLAN is seven 147 00:08:06,979 --> 00:08:08,383 and inside that tag, remember, 148 00:08:08,383 --> 00:08:11,631 there's also what we call priority bits. 149 00:08:11,631 --> 00:08:14,029 Three bits for priority. 150 00:08:14,029 --> 00:08:15,818 And the default behavior of the IP phone 151 00:08:15,818 --> 00:08:18,950 is to set that with the number of five. 152 00:08:18,950 --> 00:08:20,065 So that's what the Ethernet frames 153 00:08:20,065 --> 00:08:22,727 would look like from the IP phone. 154 00:08:22,727 --> 00:08:25,988 And then if there's a laptop connected to this, 155 00:08:25,988 --> 00:08:30,155 when it sends it's frame, well laptops and PCs by default, 156 00:08:31,479 --> 00:08:34,272 they don't do 802.1q tagging, 157 00:08:34,272 --> 00:08:37,338 so there would be no tag on here at all. 158 00:08:37,338 --> 00:08:40,914 There would just be a regular old Ethernet frame. 159 00:08:40,914 --> 00:08:44,634 So, on the switch, when this red frame comes in 160 00:08:44,634 --> 00:08:47,536 without a tag, whatever you've got configured here 161 00:08:47,536 --> 00:08:51,203 of switchport access VLAN, and I'll just put 162 00:08:53,862 --> 00:08:56,376 some number in here, let's say it's VLAN10, 163 00:08:56,376 --> 00:08:58,502 well when this red frame comes in with no tag 164 00:08:58,502 --> 00:09:02,257 it will be assigned to the broadcast domain of VLAN10. 165 00:09:02,257 --> 00:09:06,269 And when the green frame comes in that is explicitly tagged 166 00:09:06,269 --> 00:09:08,757 with the number seven, that will match up with our 167 00:09:08,757 --> 00:09:11,966 switchport voice VLAN command, and the switch will say, 168 00:09:11,966 --> 00:09:14,017 oh, OK, I can allow that. 169 00:09:14,017 --> 00:09:17,529 I know the VLAN7 is the voice VLAN. 170 00:09:17,529 --> 00:09:20,180 So that's how people typically implement voice VLAN, 171 00:09:20,180 --> 00:09:24,027 so there's a couple of other options here as you can see. 172 00:09:24,027 --> 00:09:27,860 The next option is switchport voice vlan dot1p 173 00:09:30,287 --> 00:09:31,537 so what does that mean? 174 00:09:31,537 --> 00:09:34,120 OK, so in that particular case, 175 00:09:35,211 --> 00:09:38,832 when our phone sends it's traffic, 176 00:09:38,832 --> 00:09:42,142 now it has received a CDP message saying, 177 00:09:42,142 --> 00:09:45,690 when you send something I do want you to apply a tag, 178 00:09:45,690 --> 00:09:49,098 an 802.1q tag, but I want the VLAN ID 179 00:09:49,098 --> 00:09:51,681 to actually be the number zero. 180 00:09:53,485 --> 00:09:55,971 And because you're putting that tag in there 181 00:09:55,971 --> 00:09:59,165 you're still allowed to set the priority bits in the tag, 182 00:09:59,165 --> 00:10:02,765 which by default will be the number five. 183 00:10:02,765 --> 00:10:05,329 Now by also saying dot1p we're saying 184 00:10:05,329 --> 00:10:09,160 hey, if you have a PC connected to you, 185 00:10:09,160 --> 00:10:12,156 laptops, PCs, they do have the ability 186 00:10:12,156 --> 00:10:16,323 to send frames with tags and this is called 802.1p. 187 00:10:18,545 --> 00:10:19,890 As a matter of fact, 188 00:10:19,890 --> 00:10:24,057 this priority section of the tag, that is called 802.1p. 189 00:10:25,949 --> 00:10:28,825 So if you go into the NIC card of your laptop or PC 190 00:10:28,825 --> 00:10:33,647 and you say I am enabling you for 802.1p, that means that 191 00:10:33,647 --> 00:10:37,814 laptop will now send a tag also with a VLAN ID of zero. 192 00:10:40,266 --> 00:10:43,562 It'll actually populate the VLAN of all zeros and now from 193 00:10:43,562 --> 00:10:47,729 the laptop you have the ability to set your priority bits. 194 00:10:48,630 --> 00:10:51,434 Now hopefully, whatever that priority is, 195 00:10:51,434 --> 00:10:53,904 will be something that's not five. 196 00:10:53,904 --> 00:10:56,416 It'll be something like maybe three 197 00:10:56,416 --> 00:11:00,661 because at this point the switch right here has no ability 198 00:11:00,661 --> 00:11:05,274 to, at layer two, differentiate between the voice frames 199 00:11:05,274 --> 00:11:08,191 and the data frames because they're both coming in on what 200 00:11:08,191 --> 00:11:11,242 the native VLAN is, so in this particular case, if you've 201 00:11:11,242 --> 00:11:15,409 said switchport access VLAN5 then both of these frames, 202 00:11:21,594 --> 00:11:24,875 because they don't have an explicit VLAN configured, 203 00:11:24,875 --> 00:11:28,896 both of them will go in to the broadcast domain of VLAN5. 204 00:11:28,896 --> 00:11:31,991 Now we don't have really a separate voice or data VLAN. 205 00:11:31,991 --> 00:11:34,527 They're both being lumped together into whatever your access 206 00:11:34,527 --> 00:11:38,586 VLAN is, and the only thing that makes them different 207 00:11:38,586 --> 00:11:43,082 is their layer two priority within their dot1p header, 208 00:11:43,082 --> 00:11:45,363 and also, remember, there's the layer three priority 209 00:11:45,363 --> 00:11:47,961 as well, and in the IP header 210 00:11:47,961 --> 00:11:51,389 there's the IP precedence bits, or the DSCP bits. 211 00:11:51,389 --> 00:11:55,556 So in that particular case the phone will mark it's DSCP, 212 00:11:57,025 --> 00:11:59,226 this is layer three now in the IP header, 213 00:11:59,226 --> 00:12:03,035 that's what's called expedited forwarding, 214 00:12:03,035 --> 00:12:06,141 and we'll get into that some more when we look at QoS, 215 00:12:06,141 --> 00:12:10,313 and the laptop, well, we don't know what it's going to do. 216 00:12:10,313 --> 00:12:14,485 We have no idea what it's going to do, but if the priority 217 00:12:14,485 --> 00:12:18,652 is three then the DSCP will be something that matches that. 218 00:12:19,943 --> 00:12:21,308 Something that matches this right here. 219 00:12:21,308 --> 00:12:25,843 So hopefully, at either layer two or layer three 220 00:12:25,843 --> 00:12:28,541 we'll be able to differentiate the traffic and apply 221 00:12:28,541 --> 00:12:31,866 different Quality of Service policies because at layer two 222 00:12:31,866 --> 00:12:34,967 they're both going to go into the same access VLAN. 223 00:12:34,967 --> 00:12:38,363 So that's what happens when we use the dot1p option 224 00:12:38,363 --> 00:12:41,446 in our switchport voice VLAN command. 225 00:12:43,134 --> 00:12:44,790 We're basically telling the phone, 226 00:12:44,790 --> 00:12:48,373 put a tag with a value of zero in the VLAN. 227 00:12:50,463 --> 00:12:52,278 Now what other options do we have? 228 00:12:52,278 --> 00:12:56,445 Well, what if we do switchport voice VLAN untagged? 229 00:12:57,582 --> 00:13:02,394 OK, so now what's happening, is we're telling the phone, 230 00:13:02,394 --> 00:13:05,477 so via CDP we're saying use VLAN4095. 231 00:13:08,015 --> 00:13:11,501 VLAN4095 is actually a special VLAN number. 232 00:13:11,501 --> 00:13:14,105 It's actually called the dead VLAN. 233 00:13:14,105 --> 00:13:16,518 Kind of a weird thing but it's a reserve VLAN called 234 00:13:16,518 --> 00:13:20,744 the dead VLAN and it's a way of saying don't tag anything. 235 00:13:20,744 --> 00:13:24,023 You are not allowed to use VLAN tags at all. 236 00:13:24,023 --> 00:13:26,403 So my Cisco switch now is telling the phone 237 00:13:26,403 --> 00:13:28,070 you can't do 802.1q. 238 00:13:29,198 --> 00:13:31,696 No tags allowed from you at all. 239 00:13:31,696 --> 00:13:33,159 So what does that actually look like? 240 00:13:33,159 --> 00:13:37,672 Well, in this particular case now, we would see the IP phone 241 00:13:37,672 --> 00:13:40,150 just sending a regular Ethernet frame with, 242 00:13:40,150 --> 00:13:42,483 like I said, no tag. No tag. 243 00:13:44,994 --> 00:13:48,778 But remember, at layer three in the IP header 244 00:13:48,778 --> 00:13:50,954 it's going to have all this used IP precedence 245 00:13:50,954 --> 00:13:54,650 because IP precedence is easier to understand than DSCP 246 00:13:54,650 --> 00:13:58,670 and in layer three we're going to have an IP precedence 247 00:13:58,670 --> 00:14:02,404 which is in the ToS byte of the IP header 248 00:14:02,404 --> 00:14:04,446 which is going to be equal to five. 249 00:14:04,446 --> 00:14:08,399 That's the default value that phones give at layer three. 250 00:14:08,399 --> 00:14:12,523 And if I have a laptop or PC here, well once again 251 00:14:12,523 --> 00:14:16,690 the assumption is by default laptops and PCs don't do tags 252 00:14:18,174 --> 00:14:22,678 and they don't do IP precedence, so there will be no tag 253 00:14:22,678 --> 00:14:25,205 unless someone's really messed around with their NIC card 254 00:14:25,205 --> 00:14:28,044 this will be the default behavior of the laptop or the PC. 255 00:14:28,044 --> 00:14:31,283 There will be no tag and at layer three 256 00:14:31,283 --> 00:14:34,557 the default behavior of IP precedence in every single frame 257 00:14:34,557 --> 00:14:36,520 that you send, whether it be web browsing 258 00:14:36,520 --> 00:14:39,437 or telnet or email, is always zero. 259 00:14:41,884 --> 00:14:45,372 So once again, whatever the access VLAN is here, 260 00:14:45,372 --> 00:14:49,534 switchport mode access, sorry for my sloppy writing here, 261 00:14:49,534 --> 00:14:53,701 access, equals, let's say 90, well then both of these frames 262 00:14:55,386 --> 00:14:59,015 will be assigned to the broadcast domain of VLAN-90 263 00:14:59,015 --> 00:15:01,368 and the only way we'll be able to differentiate them, 264 00:15:01,368 --> 00:15:04,178 the only way we'll be able to apply different policies 265 00:15:04,178 --> 00:15:07,015 will be based on what we see in the layer three header, 266 00:15:07,015 --> 00:15:10,019 the IP header, that will be it. 267 00:15:10,019 --> 00:15:13,908 And then of course your last option is 268 00:15:13,908 --> 00:15:18,075 switchport voice VLAN none, and that means, once again, 269 00:15:20,507 --> 00:15:25,398 there is no, I'm not giving you any VLAN or whatsoever, 270 00:15:25,398 --> 00:15:28,517 so now the IP phone doesn't really know what to use 271 00:15:28,517 --> 00:15:31,434 for a 802.1q tag, so it'll probably 272 00:15:32,441 --> 00:15:35,675 try to get that information via DHCP. 273 00:15:35,675 --> 00:15:39,493 But if DHCP doesn't give it a tag, well then at this point 274 00:15:39,493 --> 00:15:41,714 it'll be exactly the same as the previous scenario, 275 00:15:41,714 --> 00:15:43,126 as scenario three. 276 00:15:43,126 --> 00:15:47,652 If this phone is not being given a voice VLAN from my switch 277 00:15:47,652 --> 00:15:52,121 and if it's not being given a voice VLAN via DHCP 278 00:15:52,121 --> 00:15:55,547 then scenario four and scenario three 279 00:15:55,547 --> 00:15:58,964 will end up being exactly the same thing. 280 00:16:00,196 --> 00:16:02,539 So how do we verify if there's a voice VLAN, 281 00:16:02,539 --> 00:16:04,238 and if there is, what it is? 282 00:16:04,238 --> 00:16:05,127 Well we can do the command 283 00:16:05,127 --> 00:16:09,042 show interface switchport to see that. 284 00:16:09,042 --> 00:16:13,035 For example, if I go on the switch right now, 285 00:16:13,035 --> 00:16:17,202 if I do show interface fast Ethernet 0/1 switchport, 286 00:16:19,493 --> 00:16:23,493 make this a little bit larger here for you guys, 287 00:16:25,189 --> 00:16:27,290 so right now there is no voice VLAN. 288 00:16:27,290 --> 00:16:30,025 Right here, I have not configured any. 289 00:16:30,025 --> 00:16:33,876 And the default access VLAN is VLAN1. 290 00:16:33,876 --> 00:16:36,974 All I have to do is go into my interface 291 00:16:36,974 --> 00:16:41,875 and say switchport voice VLAN and I'll use VLAN2 now. 292 00:16:41,875 --> 00:16:45,668 In my case VLAN2 has not actually been created yet 293 00:16:45,668 --> 00:16:48,436 so this particular switch, like many other Cisco switches, 294 00:16:48,436 --> 00:16:52,715 will create the VLAN since it doesn't already exist, 295 00:16:52,715 --> 00:16:54,998 and now when I do that same show command 296 00:16:54,998 --> 00:16:58,947 it'll explicitly say that may voice VLAN is two 297 00:16:58,947 --> 00:17:01,017 and you can see how that's different 298 00:17:01,017 --> 00:17:04,184 than my access mode VLAN which is one.