STP Port Priority / STP between 2 switch

Seb65
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STP Port Priority / STP between 2 switch

Wed Apr 17, 2019 2:58 am

Hello,

I'm preparing to replace the Cisco switch (having redundant physical links
) for Netonix, and I have some questions
.
With Cisco I use mode rapid-pvst and spanning-tree port-priority XX


To have a priority port must the value be high or low : will a port with the value of 32 be preferred over another port at 128 ?
?


Do I have to make the same configuration on both switches regarding the priority of the ports


SW1 port 1 = 128 priority => Connected to SW2 port 1
SW1 port 3 = 32 priority => Connected to SW2 port 3





SW2 port 1 = 128 priority => Connected to SW1 port 1

SW2 port 3 = 32 priority => Connected to SW1 port 3

Thank you

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Stephen
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Re: STP Port Priority / STP between 2 switch

Wed Apr 17, 2019 1:14 pm

The lower priority will win the election process.

You don't need to change it on both sides you only need to worry about which one is the root switch.

So say for example SW1 is root

and you want port 3 on SW1 and SW2 to be the designated (or in this case the root port) and port 1 to be discarding/ the redundant link.

On SW1 set port 3's priority lower than port 1 (or like in your example port3 = 32 port 1 = 128). Since SW1 is root, the BDPU packets will carry that information to SW2 to help with it's port election process and it will see the priorities coming in on those ports and elect port 3.

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mike99
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Re: STP Port Priority / STP between 2 switch

Wed Apr 17, 2019 8:31 pm

Most would want to use cost instead of priority. Cost is also lowest = choosen path.

If I remember well, priority is only local and come after cost in root path selection.

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Re: STP Port Priority / STP between 2 switch

Sat Apr 20, 2019 6:58 am

Hello Stephen, Mike,

Here is the configuration, it is necessary that the connection AF has priority and that it is managed automatically by the Netonix switches.

For example if the AF of the tower 1 is down, the switch of the tower 1 and 2 must pass the traffic on the UBNT ISO (backup link), between the tower 2 and 3 it is necessary that the traffic pass on the AF (main link).

Is it possible to do this in order to manage two paths (Master/Main Link on AF / Backup Link on ISO 500) on the Netonix switches?

Thank you :)




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mike99
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Re: STP Port Priority / STP between 2 switch

Sat Apr 20, 2019 10:45 am

Just set an higher cost on the ports where you connect the backup link (on port 5 and 6), or set a lower one on ports 1 and 2, depending on your growing plan.

Make sure the tower 1 netonix switch, or the cisco switch, is the root switch.

To know if you should enable STP on the Cisco switch or not, we would need to see the whole network.

If STP is enabled on the Cisco switch, the're a good possibility that the Cisco switch will be root by default since the mac address will probably be lower than Netonix but I wouldn't take chance and lower the global STP priority of the switch in the Cisco. If the root switch must be the Netonix of tower 1, just lower the global priority lower than the default 32768 for the tower 1 Netonix.

Also, if doing WISP, always disable STP on ports facing customer, use loop detection instead.

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Re: STP Port Priority / STP between 2 switch

Sun Apr 21, 2019 4:01 am

Thanks Mike for the answer !

Here is the actual schema of the Cisco switch installation that will not be replaced by Netonix. The switch Cisco towers will be replaced by Netonix as indicated in my first post. Each Cisco is in stack mode
.

Here is the configuration used on Cisco (LACP / Port-Channel)
:

Code: Select all
 
vtp mode transparent
port-channel load-balance src-dst-ip
spanning-tree mode rapid-pvst
spanning-tree extend system-id
!
interface Port-channel1
 description ### TRUNK - Connected to d_SW1-1_3750G24TS [Po1] ###
 switchport trunk encapsulation dot1q
 switchport trunk native vlan 900
 switchport trunk allowed vlan 100-260,300-380,3401-3428
 switchport mode trunk
!
interface GigabitEthernet1/0/17
 description ### TRUNK - Connected to d_SW1-1_3750G24TS [Po1] ###
 switchport trunk encapsulation dot1q
 switchport trunk native vlan 900
 switchport trunk allowed vlan 100-260,300-380,3401-3428
 switchport mode trunk
 no cdp enable
 channel-protocol lacp
 channel-group 1 mode active
!
interface GigabitEthernet1/0/19
 description ### TRUNK - Connected to d_SW1-1_3750G24TS [Po1] ###
 switchport trunk encapsulation dot1q
 switchport trunk native vlan 900
 switchport trunk allowed vlan 100-260,300-380,3401-3428
 switchport mode trunk
 no cdp enable
 channel-protocol lacp
 channel-group 1 mode active
!
 




=> If the Cisco configuration is correct, now what is the correct configuration for the Netonix to have a main link and a backup link ?
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Last edited by Seb65 on Thu Apr 25, 2019 7:26 am, edited 1 time in total.

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Re: STP Port Priority / STP between 2 switch

Wed Apr 24, 2019 2:57 am

Hello,

Nobody has an idea about the configuration of the top ?

Thank you

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mike99
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Re: STP Port Priority / STP between 2 switch

Wed Apr 24, 2019 8:04 pm

If the're not multiple path between the netonix and the Cisco, STP is not needed and anyway, pvst and rstp are not compatible since pvst is cisco proprietary.

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Re: STP Port Priority / STP between 2 switch

Wed Apr 24, 2019 8:07 pm

Also, your root primary should be the device connected to the Cisco router.

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Re: STP Port Priority / STP between 2 switch

Thu Apr 25, 2019 7:32 am

mike99 wrote:If the're not multiple path between the netonix and the Cisco, STP is not needed and anyway, pvst and rstp are not compatible since pvst is cisco proprietary.


Hum... Good remark ! I have in mind to double the link between Cisco and Netonix
:thumbsup:
I wanted to migrate (in a few weeks) the Cisco <> Netonix interconnection in LACP mode
.

It seems to me that the Netonix will work in LACP mode with a Cisco no?

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