ā03-10-2019 01:57 AM
Hi
In The Topology Shown, Both PCs Are In VLAN1, The Link Between The Switches Is Configured As Trunk Allowing Only VLANs 10-100, & SW1 Is a VTP Server, SW2 Is a VTP Client.
The Two PCs Can't Ping Each Other (Obviously Because The VLAN1 Is Not Allowed On The Trunk).
My Question Is, Why Does VTP Works Fine Even Though The Native VLAN Is Not Allowed On The Trunk?
Solved! Go to Solution.
ā03-10-2019 03:43 AM
That is default behaviour by design.
On the Catalyst enterprise LAN switches, VLAN 1 is enabled by default to allow control protocols to transmit and receive packets across the network topology. However, when VLAN 1 is enabled on trunk links in a large complex network topology, the impact of broadcast storms increases. Because spanning tree applies to the entire network topology, the possibility of spanning tree loops also increases when VLAN 1 is enabled on all trunk links. To prevent this situation, you can disable VLAN 1 on trunk interfaces.
When you disable VLAN 1 on a trunk interface, no user traffic is transmitted or received across that trunk interface, but the supervisor engine will continue to transmit and receive packets from control protocols such as Cisco Discovery Protocol (CDP), VLAN Trunking Protocol (VTP), Port Aggregation Protocol (PAgP), Dynamic Trunking Protocol (DTP), and so forth.
If you using eve-ng, Right click on device and capture with Wireshark you able to view that information.
Hope make sense ?
ā03-10-2019 03:43 AM
That is default behaviour by design.
On the Catalyst enterprise LAN switches, VLAN 1 is enabled by default to allow control protocols to transmit and receive packets across the network topology. However, when VLAN 1 is enabled on trunk links in a large complex network topology, the impact of broadcast storms increases. Because spanning tree applies to the entire network topology, the possibility of spanning tree loops also increases when VLAN 1 is enabled on all trunk links. To prevent this situation, you can disable VLAN 1 on trunk interfaces.
When you disable VLAN 1 on a trunk interface, no user traffic is transmitted or received across that trunk interface, but the supervisor engine will continue to transmit and receive packets from control protocols such as Cisco Discovery Protocol (CDP), VLAN Trunking Protocol (VTP), Port Aggregation Protocol (PAgP), Dynamic Trunking Protocol (DTP), and so forth.
If you using eve-ng, Right click on device and capture with Wireshark you able to view that information.
Hope make sense ?
ā03-10-2019 07:39 AM
Thank You Very Much
ā03-10-2019 05:04 AM
a contentious subject, but my opinion is; stay away from using VLAN 1 as part of your LAN. dont default
ā03-10-2019 06:41 AM
Hi @Ali Hazim ,
Check this link:
https://learningnetwork.cisco.com/thread/89006
Maybe can help you.
Regards
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