[c-nsp] unblocking port on 3750

[Peter Rathlev]

On Thu, 2012-08-02 at 10:09 +0000, Bouazza Djamel wrote:
> Thank you for your swift reply. Hereunder the errors messages on switch 3750.
> Aug  2 06:06:07 CET: %SPANTREE-2-RECV_PVID_ERR: Received BPDU with inconsistent peer vlan id 2062 on Port-channel4 VLAN1.
> Aug  2 06:06:07 CET: %SPANTREE-2-BLOCK_PVID_LOCAL: Blocking Port-channel4 on VLAN0001. Inconsistent local vlan.
> Aug  2 06:06:22 CET: %SPANTREE-2-UNBLOCK_CONSIST_PORT: Unblocking Port-channel4 on VLAN0001. Port consistency restored.

This means that the Cisco switch, which by default assumes untagged
frames belong to VLAN 1 ("native vlan"), received a PVST BPDU belonging
to VLAN 2062 untagged. That's an inconsistency.

If this were between two Ciscos switches it could be caused by having
different native VLANs on each side. That shouldn't correct itself
automatically though.

Since the problem corrected itself I must assume that the neighboring HP
switch starts out with VLAN 2062 as untagged but switches to VLAN 1
after 15 seconds, thus restoring consistency.

> On switch 3750 :
> nterface Port-channel4
>  description *** to  CORE SWITCH  HP ***
>  switchport trunk encapsulation dot1q
>  switchport trunk allowed vlan 1-999,2010,2014,2026-2055,2060-2067,2069
>  switchport mode trunk
> 
> On Core switch HP 12508
> 
> interface Bridge-Aggregation2
>  description *** to 3750 DATACENTER ***
>  port link-type trunk
>  port trunk permit vlan 1 to 255 257 to 999 2010 2014 2027 to 2055 2060 to 2067 2069
>  link-aggregation mode dynamic

What does the physical member links look like? I'm unfamiliar with HP
swithes, but maybe the physical links have VLAN 2062 as untagged. When
they become regular members of the port-channel (LACP? Unconditional?)
they inherit the configuration from the "Bridge-Aggregation2" interface.

Maybe the configuration from the physical interfaces can shed some light
on it.

All in all I'd say that this isn't a problem as such. I just seems to
mean that the links takes 15 seconds to actually start working, but from
then it is consistent.

-- 
Peter