CCNA #029 VTP & DTP Troubleshooting for the CCNA 200-125 Exam

Key Takeaways

this is one of multiple videos discussing VTP or VLAN trunking protocol in this video we're going to troubleshoot VTP issues we've been told that when a VLAN is added to one switch in this topology it's not synchronized across the other switches in this topology we have switch 1 switch 2 and switch 3 so on switch 1 show VLAN shows us that we have the default of VLANs a VLAN 1 1002 3 4 & 5 brief shows us similar information we can see that all ports on the switch on VLAN one will ignore these unsupported old VLANs for now so let's do a test I'll create a VLAN to show VLAN briefed VLAN to exists in the VLAN database does it show on switch to so show VLAN brief we haven't learnt about of that VLAN on switch to chauvelin briefed on such three we have also not alone about that VLAN on switch three so let's start with switch 1 and switch to show VTP status the default mode in VTP is server the switch is operating as a server the default domain is null in other words no domain is configured the domain name used here is CCNA the switch is using VTP version 1 it's capable of running version one to version 3 let's have a look at switch 2 so show VTP status this looks correct the domain name is the same on both sides it's also operating as a server number of VLANs that exist it is five number of VLANs that exist here is 6 the configuration revision number is one configuration revision number is zero let's use this command show interface switch port do the same here show interface switch port ok can you find the problem [Music] what's the problem based on this output can you find the issue okay so for both of these switches on gigabit is zero zero which is the interface used by switch 1 and switch to the switchboard is enabled the administrative distance in this example is dynamic order it's the same on both sides it's currently operating as static access dynamic trunk protocol or DTP is used to automatically negotiate trunking between switches you can see that the negotiation of trunking is on but because both sides are using dynamic auto the current operational mode is static access show interface trunk shows us that there are no trunks on switch to and there are no trunks on switch 1 VT P or VLAN trunking protocol requires trunk links between switches show run interface gigabit to 0-0 this is a default configuration the switches are negotiating encapsulation they are negotiating trunking so interface trunk shows us that no trunks were negotiated show interface switch port shows us that DTP is used but it's currently set to dynamic auto on both sides on the side it's also dynamic auto which means they won't negotiate with one another and they'll revert back to access ports so what we could do here is type of switch port mode dynamic and set one side to desirable so now show interface switch port shows us that the site is dynamic it desirable the site is dynamic auto but - they've negotiated to form a trunk the operational mode is trunk the encapsulation used is ISL generally for CCNA we want to use 80221 q but on these switches which are iOS a V layer 2 switches the default encapsulation is ISL you'll find that on switches such as the 3750 as well so that looks a lot better show VTP status number of existing VLANs has increased show VLAN brief on the switch we can now see VLAN 2 in the VLAN database so let's do another test we'll create VLAN 3 chauvelin brief vielen 3 appears in the database of switch to show VLAN brief Beale entries in the database here if I create another VLAN VLAN for chauvelin brief we can see VLAN for in the database of switch one so VTP is now functioning between switch one and switch two let's have a look at switch three so show VLAN brief we still have a problem on switch three it's not learning in the VLANs through VTP so on switch three show interface trunk show interface switch port it looks like we have the same problem dynamic auto show interface gigabit zero one switch port you give it to zero one on switch to he's also using dynamic auto so let's change that to use Desirables so switchport mode dynamic desirable showed trunk or rather show interface trunk on switch to now shows us that we have a trunk port on gigabit zero zero as well as gigabit zero one the mode on gigabit zero zero is auto mode on gigabit Azera one is desirable all VLANs are permitted across the trunk current VLANs allowed and active in the management domain one to four VLANs in spanning tree forwarding state and not pruned it looks like we still got a problem here gigabit to zero zeros two to four gigabit zero one is only is only one so sure interface trunk search three has a trunk configured show interface switch port gigabit to zero zero is acting as a trunk chauvelin brief we still haven't learnt about VLANs two three and four show VTP status can you see the problem I'll show you some output on the switch so on switch two we have that output but on switch 3 we have this output can you find the problem notice VTP operating mode is transparent a transparent switch will not synchronize with other switches in the VTP domain both switches are configured in the CCNA domain but the switch is operating as a transparent to switch so and I'll just do a run first so du shall run pipe include VTP some one which is me in this case type to this command that's not the default so we need to change the mode to client or server I'll set it to server notice the configuration revision number was zero previously the number of configured VLANs was five on this side it was 8v lands and the revision number was three so now show VTP status we can see that the number of VLANs is eight the configuration revision number is three so that's been synchronized show VLAN brief we can now see the additional VLANs and now on the side if I create a new VLAN a VLAN five what should happen is we see the VLAN on both switch two as well as switch one and there we go VLAN five appears on both switch 1 and switch 2 on switch one if we create a new VLAN let's say VLAN 10 that should now appear on switch 3 and there you go so in this video I showed you two problems with VTP number one you need trunk ports so use the command show interfaces trunk to ensure that trunk ports have either been negotiated using DTP or have been manually configured also check your VDP mode transparent switches don't synchronize I hope you found it as a video useful if it's been of benefit to you please like it and please subscribe to my youtube channel I wish you all the very best [Music] you