From: wim.depauw@getronics.com
Date: Sat Aug 18 2007 - 04:49:48 ART
Hi,
I got a couple of questions about the interoperability between MST and rapid pvst.
I have the following scenario :
SW1----------------SW4
| |
| |
SW2------------------
I configured sw1 and sw2 in a MST region and sw2 is the root bridge for MST.
SW2 output
MST1
Spanning tree enabled protocol mstp
Root ID Priority 20481
Address 000e.381f.f200
This bridge is the root
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Bridge ID Priority 20481 (priority 20480 sys-id-ext 1)
Address 000e.381f.f200
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Interface Role Sts Cost Prio.Nbr Type
---------------- ---- --- --------- -------- --------------------------------
Fa0/1 Desg FWD 200000 128.1 P2p
Fa0/6 Desg FWD 200000 128.6 P2p
Fa0/7 Desg FWD 200000 128.7 P2p
Fa0/8 Desg FWD 200000 128.8 P2p
Fa0/9 Desg FWD 200000 128.9 P2p
Fa0/12 Desg FWD 200000 128.12 P2p
Fa0/13 Desg FWD 2000000 128.13 Shr
Fa0/18 Desg FWD 200000 128.18 P2p
Fa0/19 Desg FWD 200000 128.19 P2p
Interface Role Sts Cost Prio.Nbr Type
---------------- ---- --- --------- -------- --------------------------------
Fa0/20 Desg FWD 200000 128.20 P2p
Fa0/21 Desg FWD 200000 128.21 P2p
Fa0/22 Desg FWD 200000 128.22 P2p
Fa0/23 Desg FWD 200000 128.23 P2p
Fa0/24 Desg FWD 200000 128.24 P2p
I configured SW2 to work with Pvst+ and he should have his root bridge also in SW2.So I configured this on sw2
spanning-tree vlan 1 priority 20481
What I see now on SW2 is the following :
sw4#sho spanning-tree
VLAN0001
Spanning tree enabled protocol rstp
Root ID Priority 24576
Address 000e.381f.f200
Cost 19
Port 21 (FastEthernet0/19) => Interface to sw1
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Bridge ID Priority 32769 (priority 32768 sys-id-ext 1)
Address 0017.9449.4400
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Aging Time 300
Interface Role Sts Cost Prio.Nbr Type
---------------- ---- --- --------- -------- --------------------------------
Fa0/6 Desg BLK 19 128.8 P2p
Fa0/7 Desg BLK 19 128.9 P2p
Fa0/8 Desg BLK 19 128.10 P2p
Fa0/9 Desg BLK 19 128.11 P2p
Fa0/18 Desg BLK 19 128.20 P2p
Fa0/19 Root FWD 19 128.21 P2p
Fa0/20 Altn BLK 19 128.22 P2p
Interface Role Sts Cost Prio.Nbr Type
---------------- ---- --- --------- -------- --------------------------------
Fa0/21 Altn BLK 19 128.23 P2p
Fa0/22 Altn BLK 19 128.24 P2p
Fa0/23 Desg LRN 19 128.25 P2p
Fa0/24 Desg LRN 19 128.26 P2p
I see that he detects the mac-address of sw2 as root bridge => ok but he passes by sw1 to go the root bridge instead of using his direct link to sw2.
How does this come ?
gr
wim
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