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These are the user uploaded subtitles that are being translated: 1 00:00:00,000 --> 00:00:07,000 align:middle line:84% The default DTP mode depends on the Cisco IOS software version you're using 2 00:00:07,000 --> 00:00:09,000 align:middle line:84% and the platform of switch. 3 00:00:09,000 --> 00:00:14,000 align:middle line:84% In this example, I’ve got 2 switches that I've just booted up 4 00:00:14,000 --> 00:00:18,000 align:middle line:84% in other words, they have no configuration 5 00:00:18,000 --> 00:00:25,000 align:middle line:84% here switch 1 and let's change the name to S1, here’s switch 2. 6 00:00:25,000 --> 00:00:31,000 align:middle line:84% So let’s see what DTP mode the switches are using. 7 00:00:31,000 --> 00:00:39,000 align:middle line:84% You can view DTP setting by using the command sh dtp interface 8 00:00:39,000 --> 00:00:43,000 align:middle line:84% and specifying an interface, so I'll specify gigabit 0/0 9 00:00:43,000 --> 00:00:46,000 align:middle line:84% which is this link over here. 10 00:00:46,000 --> 00:00:53,000 align:middle line:84% What we can see in the output is that DTP is enabled 11 00:00:53,000 --> 00:00:57,000 align:middle line:84% the mode at the moment is access port. 12 00:00:57,000 --> 00:01:01,000 align:middle line:84% So the switch has negotiated with switch 2 13 00:01:01,000 --> 00:01:05,000 align:middle line:84% to use an access port rather than a trunk port 14 00:01:05,000 --> 00:01:10,000 align:middle line:84% and the reason why it’s because it's configured for dynamic auto 15 00:01:10,000 --> 00:01:13,000 align:middle line:84% not dynamic desirable 16 00:01:13,000 --> 00:01:18,000 align:middle line:84% as an example sh int g0/0 switchport 17 00:01:18,000 --> 00:01:23,000 align:middle line:84% shows us I'll just make this bigger 18 00:01:23,000 --> 00:01:30,000 align:middle line:84% that this port gigabit 0/0 is configured for dynamic auto as the administrative mode 19 00:01:30,000 --> 00:01:36,000 align:middle line:84% and the operational mode or mode that it's using at the moment is static access. 20 00:01:36,000 --> 00:01:42,000 align:middle line:84% DTP negotiation is on but because it’s configured for dynamic auto 21 00:01:42,000 --> 00:01:45,000 align:middle line:84% it ends up being an access port. 22 00:01:45,000 --> 00:01:55,000 align:middle line:84% Under this side show dtp interface g0/0 23 00:01:55,000 --> 00:01:59,000 align:middle line:84% you can see that it’s negotiated as an access port 24 00:01:59,000 --> 00:02:05,000 align:middle line:84% because dynamic auto is configured on the switch. 25 00:02:05,000 --> 00:02:09,000 align:middle line:84% sh int g0/0 switchport 26 00:02:09,000 --> 00:02:18,000 align:middle line:84% once again gigabits 0/0 is enabled as a switchport, it's configured for dynamic auto 27 00:02:18,000 --> 00:02:23,000 align:middle line:84% it’s operating as an access port even though DTP is enabled. 28 00:02:23,000 --> 00:02:29,000 align:middle line:84% So, let’s change that by going on to gigabit 0/0 29 00:02:29,000 --> 00:02:33,000 align:middle line:84% and typing switch port and we have a few options 30 00:02:33,000 --> 00:02:36,000 align:middle line:84% so let’s say mode dynamic 31 00:02:36,000 --> 00:02:41,000 align:middle line:84% which is setting the trunking mode to dynamically negotiate access 32 00:02:41,000 --> 00:02:46,000 align:middle line:84% or trunk mode and we can either use auto or desirable 33 00:02:46,000 --> 00:02:48,000 align:middle line:84% so I’m gonna configure this is desirable 34 00:02:48,000 --> 00:02:55,000 align:middle line:84% so previously on switch 1 when we type sh int g0/0 switchport 35 00:02:55,000 --> 00:02:59,000 align:middle line:84% it was operating as a static access port. 36 00:02:59,000 --> 00:03:01,000 align:middle line:84% What is it doing now? 37 00:03:01,000 --> 00:03:05,000 align:middle line:84% so sh int gigabit 0/0 switchport 38 00:03:05,000 --> 00:03:12,000 align:middle line:84% this side is using dynamic auto but the mode negotiated is a trunk port 39 00:03:12,000 --> 00:03:19,000 align:middle line:84% using the ISL encapsulation, it’s not using 802.1Q its using ISL. 40 00:03:19,000 --> 00:03:24,000 align:middle line:84% On this side sh int g0/0 switchport 41 00:03:24,000 --> 00:03:30,000 align:middle line:84% notice this side is dynamic desirable switch 1 is dynamic auto 42 00:03:30,000 --> 00:03:34,000 align:middle line:84% but we've configured switch 2 to use desirable 43 00:03:34,000 --> 00:03:37,000 align:middle line:84% so switch 2 initiated trunking with switch 1 44 00:03:37,000 --> 00:03:44,000 align:middle line:84% and it negotiated to use ISL and hence it becomes a trunk 45 00:03:44,000 --> 00:03:48,000 align:middle line:84% so when both sides are configured for auto it doesn’t become a trunk 46 00:03:48,000 --> 00:03:52,000 align:middle line:84% when 1 side is configured for auto 47 00:03:52,000 --> 00:03:56,000 align:middle line:84% and the other side is using desirable a trunk will be formed. 48 00:03:56,000 --> 00:03:58,000 align:middle line:84% So once again to prove that 49 00:03:58,000 --> 00:04:01,000 align:middle line:84% let's go back into the interface 50 00:04:01,000 --> 00:04:06,000 align:middle line:84% and I'll change the mode to auto 51 00:04:06,000 --> 00:04:09,000 align:middle line:84% I'll shut it down and then no shut it 52 00:04:09,000 --> 00:04:11,000 align:middle line:84% so that they can negotiate once again 53 00:04:11,000 --> 00:04:18,000 align:middle line:84% on this side notice static access it is no longer a trunk 54 00:04:18,000 --> 00:04:25,000 align:middle line:84% and on this side once again notice it's using a static access port 55 00:04:25,000 --> 00:04:29,000 align:middle line:84% because neither side are initiating trunking 56 00:04:29,000 --> 00:04:33,000 align:middle line:84% the port remains an access port and doesn’t become a trunk. 57 00:04:33,000 --> 00:04:41,000 align:middle line:84% If either side or both sides are configured 58 00:04:41,000 --> 00:04:49,000 align:middle line:84% to use desirable the port will become a trunk port. 59 00:04:49,000 --> 00:04:53,000 align:middle line:84% So let’s configure on both sides as dynamic desirable 60 00:04:53,000 --> 00:04:57,000 align:middle line:84% I'll shut it down and then no shut it 61 00:04:57,000 --> 00:05:02,000 align:middle line:84% sh int g0/0 switchport 62 00:05:02,000 --> 00:05:09,000 align:middle line:84% both side are configured for dynamic desirable 63 00:05:09,000 --> 00:05:14,000 align:middle line:84% so the link has become a trunk port 64 00:05:14,000 --> 00:05:20,000 align:middle line:84% you can also use the command sh int trunk 65 00:05:20,000 --> 00:05:24,000 align:middle line:84% and as we can see here gigabit 0/0 is a trunk port 66 00:05:24,000 --> 00:05:30,000 align:middle line:84% mode is desirable and the encapsulation is ISL native VLAN is 1 67 00:05:30,000 --> 00:05:33,000 align:middle line:84% all VLANs are allowed across the port 68 00:05:33,000 --> 00:05:37,000 align:middle line:84% we'll see something similar on switch 1 69 00:05:37,000 --> 00:05:39,000 align:middle line:84% so sh interface trunk 70 00:05:39,000 --> 00:05:42,000 align:middle line:84% notice desirable ISL is being used 71 00:05:42,000 --> 00:05:50,000 align:middle line:84% I'll set this side back to auto 72 00:05:50,000 --> 00:06:01,000 align:middle line:84% shut it down, no shut it, do sh int trunk 73 00:06:01,000 --> 00:06:11,000 align:middle line:84% sh int trunk we haven't got a trunk configured at the moment. 74 00:06:11,000 --> 00:06:14,000 align:middle line:84% Let’s see this side show interface trunk 75 00:06:14,000 --> 00:06:22,000 align:middle line:84% took a while but it's now negotiated to use a trunk with switch 2 76 00:06:22,000 --> 00:06:25,000 align:middle line:84% the mode on the left is auto 77 00:06:25,000 --> 00:06:28,000 align:middle line:84% the mode on the right is desirable. 78 00:06:28,000 --> 00:06:31,000 align:middle line:84% So these 2 switches on gigabit 0/0 79 00:06:31,000 --> 00:06:34,000 align:middle line:84% have negotiated to use trunking 80 00:06:34,000 --> 00:06:41,000 align:middle line:84% because 1 side in this case switch 2 is initiating the trunking. 81 00:06:41,000 --> 00:06:47,000 align:middle line:84% However, we change that again to auto. 82 00:06:47,000 --> 00:06:52,000 align:middle line:84% sh int trunk 83 00:06:52,000 --> 00:06:55,000 align:middle line:84% we don’t see any trunking. 84 00:06:55,000 --> 00:06:58,000 align:middle line:84% On this side, we don’t see any trunking. 85 00:06:58,000 --> 00:07:05,000 align:middle line:84% If we look at the interface you can see it’s an access port 86 00:07:05,000 --> 00:07:10,000 align:middle line:84% so no trunking is taking place. 9561