3750 stacking or MSTP

[vovochka83]

Hi,

Currently our setup as below:

Currently is running pvst + on Cisco switch, but the HP switch is running on mst. So how should i make the HP switch redundancy and at the same running proper STP with Cisco (if possible without configuration all Cisco to MSTP..)? If i add stack another switch into level Cisco switch then i will lost the redundancy to level 2 as below, btw level 1 and level 2 switches is not stacking together just port channel:

[dukenuk96]

Hi!

You enable stacking on Level 1, but why do you move link from HP-Level2? Leave it right there where it was - if stack will fail for samo reason (in practice it happens), you will loose connectivity for HP users. Also I would recommend you to migrate to MSTP on all of the switches - so you will have predictable convergence and won't need to debug two different protocols. Migrating to MSTP is not very difficult. I assume that stacked switches are represent core of your network, so general configs for MSTP would be:

3750 Level 1:

spanning-tree mode mst

spanning-tree pathcost method long
spanning-tree mst 0-1 priority 4096
spanning-tree mst configuration
  name <here is you region name, must be same on all switches>
  revision 1
  instance 0 vlan 1
  instance 1 vlan 2-3500

3750 Level 2:

spanning-tree mode mst

spanning-tree pathcost method long
spanning-tree extend system-id
spanning-tree mst 0-1 priority 8192
spanning-tree mst configuration
  name <here is you region name, must be same on all switches>
  revision 1
  instance 0 vlan 1
  instance 1 vlan 2-3500

Plus all ports used for end-users connections should have:

spanning-tree portfast

Not sure for HP what config should look like, you need to read vendor's manual - leave bridge priority default or make it 16384 for example, since you are not going to use HP switch as your network core, right?. Also if you want to use either link simultaneously and loab balance two uplinks from HP switch between VLANs, the configuration will differ.

Then remove all pvst+ configurations from 3750 switches and test that redundancy works and how fast it works - the delay to failover should be sub-second, bot for now I suggest it takes about 45 seconds, due to different protocols operation and pvst+ will work in this manner if you will not enable *fast* features.

[vovochka83]

So you suggest to migrate MSTP, then how about the instance 0 vlan 1? We are not using vlan 1 in our network and int vlan 1 is shutdown...

[dukenuk96 · Accepted solution]

Yes, MSTP is easier to configure and standard IEEE protocol, it almost always operates same way on different vendors.

You do not use VLAN 1 for your production traffic - that's good, you can even skip the string "instance 0 vlan 1" but it will still be present, because any VLANs that were not assigned a specific instance, will be by default assigned to instance 0. Example of my working switch follows.

Config:

spanning-tree mode mst
spanning-tree extend system-id
spanning-tree pathcost method long
!
spanning-tree mst configuration
 name sd1
 revision 1
 instance 1 vlan 2-3500
!
spanning-tree mst 0-1 priority 61440

Diag:

SD1-1-1-3-L2SW-10#sh spanning-tree mst configuration
Name      [sd1]
Revision  1     Instances configured 2

Instance  Vlans mapped
--------  ---------------------------------------------------------------------
0         1,3501-4094
1         2-3500
-------------------------------------------------------------------------------

So you can see - I even did not touch instance 0, there are some VLANs (actually not used in my network). Even when you enter command "instance 0 vlan 1" - you will not see it in your running config (checked), I just provided this command for you to be sure that vlan 1 will be in instance 0 if you or someone else already configured different.

Even more - CDP, STP, LLDP, etc.. link-layer protocols are all work in default VLAN 1, so even if you shut VLAN 1 interface, the VLAN itself still will be working.