I was just going thru a documentation abt disabling vlan 1 on trunks,I came across the following lines...
"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"
My doubts are..
1) How can enabling vlan 1 on trunks increase the possibility of spanning tree loops...?
2) I have read that VTP,CDP etc is using VLAN 1 for its propogation,and how will the supervisor engine receive the VTP,cdp if vlan 1 is disabled on the trunk..?
Thanks in advance..