We help IT Professionals succeed at work.

Recommendation on selecting Root switch

Rick_Penney
Rick_Penney asked
on
141 Views
Last Modified: 2016-09-13
TopologyHi
I am about to change all our switches and have pre configured spanning-tree and bpdu protection on all the switches.
I have simplified the drawing by removing a lot of switches, however all switches will connect back to switch 1 with a single crossover cable.
Spanning-tree with Portfast / Admin Edge Port and BPDU protection is configured on all ports with the exception of the uplinks.
I have a question about setting the root switch. I plan to set the bridge priority of switch 1 to have a value of 16384, all other switches are set to default. Would this be the recommended switch to set this on?
Do I also need to set a value of 16384 on the Cisco switch 5 for interface vlan 2?
Kind regards
Rick
Comment
Watch Question

Michael OrtegaDirector of Sales Engineering, Americas
CERTIFIED EXPERT

Commented:
If Switch one is going to be your main agg switch then it should be your root bridge. If it's also going to traverse vlan 2 traffic then it should also be the root for that segment as well.

For Cisco switches the default value for the bridge priority is 32k+. I would think it was a general standard default amongst other switch vendors as well.

MO

Author

Commented:
Hi Michael, many thanks for your reply.
My primary and secondary (backup) routers do both connect to the same switch 1, so all traffic does go through that switch.
I don't however have any config on the switch 1 relating to vlan2. Traffic knows to get to vlan2 via a static route on the router to tell it to go through switch 5.
So, for me to make switch 1 the root for vlan 2 as well, will I just need to add a vlan 2 interface to the HP switch 1 and tag both vlans to the port on switch 1 that connects to switch 5?
Many thanks
Rick
Michael OrtegaDirector of Sales Engineering, Americas
CERTIFIED EXPERT

Commented:
I'm confused. In your diagram, it shows that Switch 5 trunks to Switch 1. I'm assuming it sends the VLAN2 segment through the same link before it hits your Router(s)? Or do you have a separate link on Switch 5 that connects directly to your Router?

MO

Author

Commented:
Hi, sorry I was trying to condense our network in the drawing I embedded.
There is actually a switch in between 1 and 5 .
The port that goes from this other switch to switch 5 is set up as a trunk for both vlans.
The port that goes from this other switch to switch 1 isn't set up as a trunk port.
switch-config2.JPG
Michael OrtegaDirector of Sales Engineering, Americas
CERTIFIED EXPERT

Commented:
Ok, so switches 5 & 6 carry both VLAN1 & 2 over to the intermediate switch. The intermediate switch connects to Switch 1. You specify that it's not trunked to Switch 1, but you are passing VLAN1 traffic from the intermediate to Switch one via the link illustrated, right? You're just not passing VLAN2 traffic? If not, where does VLAN2 traffic go beyond the intermediate switch? Anywhere?

MO
CERTIFIED EXPERT
Distinguished Expert 2018

Commented:
Cisco and HP run incompatible versions of STP. You should use MSTP in mixed environment.
ProCurve & Cisco Spanning Tree Interoperability
And missing switches in drawing for STP are not good idea. Don't forget that max diameter of STP is 7 "hops" (end-to-end anywhere should not be more than 7 switches) and with that said from Cisco switch 1 to Cisco switch 6 is 4 "hops". Diameter actually can be more than 7 hops, however it is not recommended.

Author

Commented:
Hi Michael
The intermediate switch does connect to switch 1 from its port 1.
There is no config on port 1, however traffic from both subnets from vlan 1 and 2 on the other two switches are able to pass through to Switch 1.
!
interface GigabitEthernet0/1
!
Every switch on our network is able to ping every device on switches 5 & 6

Hi Predrag Jovic
Many thanks for your comments and link. I will print this out tomorrow and have a read through.
The only reason that its configured like that is switch 1 is currently an old cisco 2950 24 port. The intermediate switch is a 2960 and connects to switch 5 via a fibre link as its in a different comms room. I appreciate the guidance though.
Michael OrtegaDirector of Sales Engineering, Americas
CERTIFIED EXPERT

Commented:
Rick,

What that means is that the connection between the intermediate switch and Switch 1 is automatically trunking and the default behavior is to allow all VLAN traffic through.

MO

Author

Commented:
Thanks Michael, I'm very grateful for your time and knowledge.
Just to go back to your comment ref the root switch for vlan2, shall I make it the intermediate switch or switch 1?.
I will be leaving 6 cisco switches in place as they are quite new Gigabit switches. The rest will be replaced with HP, so it looks like I've got of extra learning to do on the Cisco / HP compatibility front :-)
regards
Rick
Michael OrtegaDirector of Sales Engineering, Americas
CERTIFIED EXPERT
Commented:
This problem has been solved!
(Unlock this solution with a 7-day Free Trial)
UNLOCK SOLUTION
CERTIFIED EXPERT
Distinguished Expert 2018
Commented:
This problem has been solved!
(Unlock this solution with a 7-day Free Trial)
UNLOCK SOLUTION

Author

Commented:
Many thanks to you both for your help with this.
My reason for the "Best Solution" was for the HP side of things, although I'm aware Michael posted a lot of helpful replies so a massive thank you to you too.
Regards
Rick