Bridge Priority

[simonator]

Hello again,

I just want to ask how can I configure bridge priority of a Cisco Switch. I have a Cisco 4506-e L3 Switch and I want it to be the root switch/bridge.

I also want to know if there are any bad effects or negative effects when I configure this to the Cisco 4506-e which also acts as a DHCP server and router for the whole LAN.

Thank you.

[Joseph W. Doherty]

Disclaimer

The Author of this posting offers the information contained within this posting without consideration and with the reader's understanding that there's no implied or expressed suitability or fitness for any purpose. Information provided is for informational purposes only and should not be construed as rendering professional advice of any kind. Usage of this posting's information is solely at reader's own risk.

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In no event shall Author be liable for any damages whatsoever (including, without limitation, damages for loss of use, data or profit) arising out of the use or inability to use the posting's information even if Author has been advised of the possibility of such damage.

Posting

e.g.

#### Configuration only to be applied to ROOT ####

!

spanning-tree vlan 1-1004 priority 8192

Bad effects, no.

[simonator]

Thanks for the Reply Mr. Joseph,

I just want to clarify something. What do you mean by this? :)

#### Configuration only to be applied to ROOT ####

What if I want to make a switch that is not a root to be THE root? In my case my DHCP server/L3 Switch. Maybe I want to make it a priority of 1?

[Joseph W. Doherty · Accepted solution]

Disclaimer

The Author of this posting offers the information contained within this posting without consideration and with the reader's understanding that there's no implied or expressed suitability or fitness for any purpose. Information provided is for informational purposes only and should not be construed as rendering professional advice of any kind. Usage of this posting's information is solely at reader's own risk.

Liability Disclaimer

In no event shall Author be liable for any damages whatsoever (including, without limitation, damages for loss of use, data or profit) arising out of the use or inability to use the posting's information even if Author has been advised of the possibility of such damage.

Posting

You cannot set priority to 1.  Lowest (best) value is 4096, and increments by 4 K.

[simonator]

Mr Florin and Mr. Joseph,

I need your help. My network is messed up bigtime.

I have a port configured to access vlan 7 but its getting an IP from vlan 5. The Core Switch is acting as the DHCP server and is VTP status Server while the Server switch is connected to the Core Switch with VTP status transparent. Everything was normal before 2 weeks ago. But now I have to do ipconfig /release and renew or restart the computer to get the right IP. Can you please tell me whats going on.

I also checked the stp ports and when I check the Server Switch I saw that the interface was an access port.

I have attached some topology and screenshot of my switches. Thank you for your help.

[simonator]

Hey mates,

I discovered something when Im troubleshooting it. My core switch is flapping between vlans!

I don't know what to do. Here is the result

[Florin Barhala · Accepted solution]

show interface .... switchport for the Vlan7 port what does it tell us?

[Florin Barhala · Accepted solution]

Hi mate,

I was there before with setting priority as low as possible, I could think of -1 maybe :).

So spanning-tree vlan 1-4094 priority 8192 should do it for you for now. You always have to take care of your network and know what devices you add.

About DHCP server? It's probably a good idea, still if you a have down the tree (linear) topology it wouldn't matter that much where exactly is the root bridge.

Contrary it matters, when you start using multiple redundant path on your topology. Also don't forget updating each switch flavor to RSTP.