Spanning Tree Nexus

[opnineopnine]

Hi all,

I have to connect via L2 a 6509 with a nexus 7700 series, regarding the Spanning tree configuration what will the best practices be for this integration?

Thanks.

140

[devils_advocate]

It depends really.

Which of the two switches are connected to an existing network with STP enabled?

Are you connecting a single link between them or two links?

The best practices will depend on the topology. 

[opnineopnine]

hello

the 6509 is the one that is connected to the existing network, the idea is to migrate all to the 7700, but for now i will just expand via L2.

[devils_advocate]

What is the current root bridge for the network which the 6509 is connected to?

What mode of STP are you running?

Assuming the STP of the existing network is configured optimally then adding a new L2 switch should not cause any issues as long as you follow best practice.

[opnineopnine]

In the 6509 the customer is using rapid-pvst.

thanks. 

[pwwiddicombe]

There are some quirks with spanning-tree between nexus and non-nexus.  Read up on Edge / network / normal spanning tree on nexus ("bridge assurance").  If you have multiple links (redundancy) between nexus and 6509, there is a chance that the nexus STP will block a port to the 6509 but still send bpdu's on the blocked port, which is different to the behavior on the 6509. 

[opnineopnine]

Hello

I will have to links one to each nexus.  Is there any chance you can post a config for the the Nexus?

Thanks. 

[opnineopnine]

Hi all,

I conected my 7700 to the 6500, both ports from the 7700 and the 6500 are in (Root FWD)

I configured the inteface with spanning-tree

  "spanning-tree port type normal"

will this be ok?

thanks all.

384

[pwwiddicombe]

"both ports..."

Do you have multiple links between the 7700 and 6500? 

If so, are they a port channel?

If they are, then it is a "single logical link"; and if that is the case then you wouldn't run into the spanning-tree issue, unless there are also OTHER paths in the network that traffic could get between the two.

[opnineopnine]

Hello, There are to logical links one to each device and I have this output in the 7700

7700k-1

Vlan             Role Sts Cost      Prio.Nbr Type
---------------- ---- --- --------- -------- --------------------------------
VLAN0999         Altn BLK 2         128.174  P2p

!

7700k-2

Vlan             Role Sts Cost      Prio.Nbr Type
---------------- ---- --- --------- -------- --------------------------------
VLAN0900         Root FWD 2         128.174  P2p

And this is how its connected

7700 ------6500-01

  ||vpc

7700 ------6500-02

Thanks.

140

[opnineopnine]

hello,

Do you have any doc about best practices for this?

thanks.