Cisco vlan trunking and spanning tree protocol

[mezta21]

Hi, fellas is there anyone here who can help me regarding Vlan trunking and Spanning tree protocol.?
I'm designing a network consist of 610 nodes and I'm using Catalyst 2960 48 ports Switch and Router 2900 series
for my gateway. In every Catalyst switch it has 6 Vlan ID including Vlan 1 which is the default Vlan. The thing is
when I'm not yet configuring a Vlan ID I set the core switch 4500-e as a primary root bridge on Vlan 1 and leaving the other
edge switches as pre configured and it seems like everything is running smooth. I saw some of the switches are on the Blocking mode and Designated port. But when I started to configure Vlans on every switches the problem came up, all the blocked ports became open and as we know spanning tree is very important to avoid switching loops. And when I show the spanning tree result it shows that out of 6 Vlan ID I have 4 vlan that it says that all of them are root bridge like "VLAN 10 This Bridge is the root" "VLAN 20 This Bridge is The Root". and as we know in spanning should have only 2 root bridge the PRIMARY and SECONDARY, so my question is should I turn off the spanning tree to all the vlan ID that I've created and leave only VLAN 1 has spanning tree wich all my trunkport are assigned? and which Vlan ID should I assign my trunkport for all the switches including the core switch. I hope you can help me fellas for this issue.

Thank you,

Happy Valentines,

 

[pndscm]

Cisco's run per PVST or Per VLAN Spanning Tree. You should set up your 4500e as the root bridge for all the vlan's.

 

[mezta21]

I absolutely understand that I need to assign my Core switch as Root bridge for all the vlan. But my question is in what Vlan ID shoud assign my root bridge? I have 6 Vlan ID (Vlan 10 20 30 40 50) as of now all my trunk port are all assign in VLAN 1. I used the Command
"Spanning Tree Vlan 1 root Primary" and after that I run the command Show SPT and the result is my core switch is now the root bridge.
but when I check my edge switches which I configure Vlans it shows that out of 6 vlan that I created 4 of them are root bridge. I ask a friend of mine and he told that turn of all the VLANS except the management Vlan or Vlan 1 were all my trunk ports are assigned. But the thing is he is not also sure if that is the right way. please fellas if there someone who can help me to overcome this problem I will really really appreciate.

Thank you,

 

[imbadatthis]

so your switches are showing root vlan probably cause you are not TRUNKING the vlans to the other switches. at least that is what im reading there.

1 - make sure all you 'uplinks' are trunks
'swi mod tru
swi tru all vlan 10,2030,40,50
no shut
'

2 - make sure that your 4500e is the root for all vlans.
just bring the priority of that device down to 4096 and it should become root.


---
optional - good to do:

all ports connected to a phone / PC :
make them port-fast

all ports connected to your 4500e:
enable:
bpdu guard
root guard

-----



We must go always forward, not backward
always up, not down and always twirling twirling towards infinity.

 

[mezta21]

HI imbadatthis thank you for sharing your good idea I will try that tomorrow at the site. But as i've said all the trunk line has been set to trunk mode. What I mean trunk line is the port I used to connect to the core switch, but what I did are all that trunk line are being assign to VLAN 1. I tried to apply the command No Spanning-Tree to all the VLAN ID that I created except Vlan 1, as i've said recently that I assign all my trunk port and it shows that I have achieved the output that I desired. But I'm not sure if that is the right way to overcome the problem.

 

[imbadatthis]

you can't delete vlan 1.
if you use the command i gave you for trunk it will remove it as a trunked vlan .

you can also create a vlan for your black hole and additional security - i use vlan 666:

conf t
vlan 666
name VL666-BLACKHOLE

and on all your trunk ports :

swi tru nat vl 666


this with combination of my original config for your trunks will remove vlan 1 from being anywhere near a trunk

We must go always forward, not backward
always up, not down and always twirling twirling towards infinity.