uplink issue

[Robo123]

Hi ,

Please find attaached diagram.
We are running MSTP in core switch and RSTP in distribution.
I have a server which is in vlan 128.currently the traffic is passing through core sw2.(HSRP priority 110)
As per stp "core sw1" is the rootbridge for vlan 128 were we can observe the GI 11/43 ,GI 11/43 ports connected from core sw1 to dell sw1 is in "alternate blocking " state.

#sh spanning-tree

MST1
Spanning tree enabled protocol mstp
Root ID Priority 1
Address <------->
This bridge is the root

Gi11/43 Altn BLK 20000 128.1323 P2p Bound(RSTP)
Gi11/44 Altn BLK 20000 128.1324 P2p Bound(RSTP)

can any one clarify why the rootbridge port is in blocking state.

[Georg Pauwen]

Hello,

not sure how accurate your drawing is, but the way you have laid it out, it looks like there is only one path from each HSRP device. If core switch 2 is the active HSRP, then there is only that one path. Core switch 1 is in standby mode and won't forward any traffic...

Maybe I misunderstand what you are asking...can you post the configs of your switches ?

[Robo123]

Hi George,

Thanks for the replay.

The query is.

+ I have 2 cisco 6513(core SW1,SW2) both are configured HSRP.
+ For core sw1 --> standby 128 priority 105 configured in HSRP
+ For core SW2 --> standby 128 priority 110
+ Server is in Vlan 128.
+ when we are trying to ping from server to outside network packet is going through Core SW2 (Reason--> standby 128 priority is 110 )
+ Both core switch are running MSTP and in distribuion (Dell switch) running RSTP.
+ As per spanning tree output core switch 1 is root bridge for vlan 128 at same time we can observe Gi11/43, Gi11/44 which is connected from core sw 1 --> distribuion(dell sw1)ports are going for Altn BLK.
+ In net working we are using load sharing mechanism.

Hope this is clear.Please clarify why the rootbridge port is in ALT blocking state.

[Georg Pauwen]

Hello,

I have played around with different spanning tree mode setups, but I haven't been able to get a port in ALTN BLK state, which is fine actually, since that state isn't supposed to happen on a root device.

So, it could be a bug...can you post the output of 'show ver' of the 6513s ?

If possible, try and combine the ports into a port channel...and check if the state changes.

[Robo123]

Hi george,

Running ios is "s72033-adventerprisek9_wan-mz.122-33.SXJ10.bin"

[Georg Pauwen]

Hello,

I checked for bugs but couldn't find any related to what you are seeing. If this is a production network, you probably cannot experiment a lot, but two things you could try is to use RPVST+ instead of MST on the Cisco switches, or upgrade to a 15.x code...

[Robo123]

Hi,

If we aar running Mstp in cisco end and Rstp in dell switch end how the election will happen is there any changes will happen if dell switch will is using in distribution 

[Georg Pauwen]

Hello,

as I understand it, running STP in multi vendor environments can render unpredictable results. Depending on which Dell switches you have, check if they support SSM (Simple Switch Mode).

I would at the very least manually configure the primary and secondary root on the Cisco switches.

Have a look at the attached document as well.

Dell-Cisco STP Interoperability and Recommendations