Hello,
in these days I am learning about STP(PVST+) and I got some questions. I would be really thankful for anwering them.
I created redundant topology with some switches using VLAN10, 20, 30 and 90. Because of security I put native VLAN into some unused VLAN, in this example into 999. So I decided to not use this native VLAN, just configure it as native on trunks and allow there only 10, 20, 30 and 90. VLAN 1 and 999 dont have any end nodes. Here is example of configuration.
interface FastEthernet0/1
switchport trunk native vlan 999
switchport trunk allowed vlan 10,20,30,90
switchport mode trunk
1) So that means through trunks configured like this will pass only trafic from VLAN10, 20, 30 and 90 + management traffic from VLAN1, like VTP and other protocols cisco uses in VLAN1. No data traffic from VLAN1. Also there shouldnt be any VLAN999 traffic passing trunks, because it is not allowed. Am I right?
Next, I configured primary root switch:
spanning-tree vlan 10,20,30,90 priority 4096
And secondary root switch:
spanning-tree vlan 10,20,30,90 priority 8192
2) Every root switch for VLAN 10,20,30 and 90 works good. But, there I found a problem. VLAN999 in this topology found its own root switch too. It was random switch because every switch for this VLAN got priority 33767, it is normal, every other switch for VLAN999 became non-root. But how this happened, when I didnt allow traffic for this VLAN on trunks? Is it normal? Or am I wrong? BPDU are sent over their VLANs, no? So if there are not allowed VLAN1 and VLAN999 on trunks, they wont be able to send their BPDUs through them. So why then VLAN999 created its own STP topology and VLAN1 not? How to prevent this if I want to remove this VLAN999 STP topology, if it is possible.
3) Also on switches, that have etherchannel I found this kind of output for VLAN10,20,30 and 90 with 4 interfaces listed. Portchannel 1 consists of Fa0/1 and Fa0/2. So output is correct.
VLAN10
Fa0/4 Desg FWD 19 128.4 P2p
Fa0/3 Root FWD 19 128.3 P2p
Gi0/1 Desg FWD 4 128.25 P2p
Po1 Altn BLK 9 128.27 Shr
And this for VLAN999. Why is it showing me Po1 and his interfaces Fa0/1 and Fa0/2 too? Is it problem?
VLAN999
Fa0/1 Desg FWD 19 128.1 P2p
Fa0/4 Altn BLK 19 128.4 P2p
Fa0/3 Root FWD 19 128.3 P2p
Fa0/2 Desg FWD 19 128.2 P2p
Gi0/1 Desg FWD 4 128.25 P2p
Po1 Altn BLK 9 128.27 Shr
Please correct me and help me, I am really getting lost in this. Also sorry for my English, I think I made some mistakes. Thanks.
