ASR9000 Layer 2 Integration with 7600

[IT-cocoon]

Hello,

I have a problem integrating 2 x ASR9000 with 2 x 7600

The topology is Just simple

A9k--------A9K

|              |

7600------7600

ASR 9000 is running MST , while 7600 is running PVST all attached using a Single Tengig Interface.

The problem I have that i can see there are two roots - A root per each Protocol Rootbridge for MST and root for PVST

Is there a specific best practice for integration in such, I need to run it  using spanning tree , as PVSTAG will not be included in spanning tree Algorithm , and i was not able to connect a server dual homed to the two 9ks.

Thanks!

[Bryan Garland]

Rando,

The mixing of STPs can get tricky.  Now depending on your MST config you could see a root for MST CIST and then different roots for the PVST vlans that are not included in the CIST.

Here is a decent doc on MST and integrating it with PVST.

http://www.cisco.com/en/US/tech/tk389/tk621/technologies_white_paper09186a0080094cfc.shtml

Simply put, we should see all roots in MST region or just CIST in MST and ALL other vlans not included in CIST need to be seen as a root in MST or PVST.  Can't be mixed. 

If you want to include snippets of your MST and PVST configs we can look at it further.

Thanks,

Bryan

[IT-cocoon]

On both ASR9K:

spanning-tree mst Trust_sig

name Trust_sig

revision 1
instance 0
   priority 32786
!
instance 1
   vlan-ids 100,200
   priority 32786

!

interface GigabitEthernet0/0/0/2

!

interface GigabitEthernet0/1/0/2

!

l2vpn

bridge group Trust_sig

bridge-domain Trust_sig1

interface GigabitEthernet0/0/0/2

interface GigabitEthernet0/1/0/2

On 7600 its normal PVST configuration with priority 0 on 7600(1)

Is there any specific thing i need to do from PVST side or from MST side? also now i am having a spanning tree loops.

I need to insure interoperability between both sides , and also that 7600(1) always act as the root for vlan 100 and vlan 200