[c-nsp] Nexus 7018 spanning tree and unicast flooding

[Quinn Snyder]

prashanth --

i see that you have all ports as 'network' ports. i assume this is
done by invoking

spanning-trew port type network

under the interface configuration stanza or so. in n7k land, this
invokes a feature called 'bridge-assurance' and it must be explicitly
enabled on the other end. it is a feature that can only be enabled
globally on n7k and is enabled by default if you run any vpc services
on n7k.

that being said -- your issue may be caused by this configuration
statement. bridge-assurance is only supported on certain versions of
c6k, so i'd say that you have to change this. [0]

please set all ports that dont have bridge-assurance on both ends to
the following

spanning-tree port type normal

and see if this solves your problem.

regards,
q.

[0] https://supportforums.cisco.com/thread/2000819

-= sent via ipad. please excuse brevity, spelling, and grammar =-

On Jun 27, 2011, at 11:05, Prashanth kumar <smarni7468 at gmail.com> wrote:

> I am trying to troubleshoot a issue with  spanning tree topology change and
> unicast flooding during the topology change which I have not seen in 6500.
> I am new to nexus series.
>
> +----------+                            +-------------+
> |              |                             |                |
> | Root     |                             | Secondry |
> | SW1     |------------------------| Root        |
> |              |------------------------| SW2       |
> +----------+                            +------------+
>     |                                      /
>     |                                 /
>     |                             /
>     |                 span blocked
> +-------------------/---+
> |  Access Switch   |
> |                            |
> +----------------------+
>
> We have a simple topology of two Nexus 7018  aggregation routers in DC and
> access-switches connected to two of them as shown above. There are multiple
> VLAN's trunked to the access  switches.  All vlans are trunked between Nexus
> switch as well.  The Access swtich connection to
> second 7018 is blocked.  We run PRSTP+ and all ports on core switch are type
> network.  The issue we have is when ever we bring up a new port  or port
> state changes on 7018 there is TCN generated and both the switch flush the
> cam table and it takes about 15 to 30 second to re-learn the new mac. during
> this time we see lot of unicast flooding on all the switches/load balancer
> which are connected. Is this a limitation on Nexus 7000 or is this normal
> behavior. I have not seen this on 6500.
>
> Thanks you in advance
>
>
> PK
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