Vice versa for Core2 to become the Root Bridge for VLANs 20 and 99:
Finally, the port costs for the connections to the GbESMs are set to a higher value to make them relatively undesirable Spanning Tree Paths. This is to ensure that the direct connection between the Core switches is preferred:
interface
Reenable the ports
After verifying the correct cabling between the all the devices, the ports can be enabled:
Enabling the ports on GbESM_1 and GbESM_2
/oper/port EXT1/ena /oper/port EXT2/ena /oper/port EXT5/ena /oper/port EXT6/ena
Enabling the ports on Core1 and Core2
conf t
int range
Verify the Spanning Tree status
Verify the port status and vlan assignment by typing the info/link and info/port command on the GbESM. The commands info/l2/stg and info/l2/trunk shows the Spanning Tree status. Verify that no ports of the GbESMs are in BLOCKING status since the Spanning Tree is disabled.
For Cisco IOS devices some commands you can use to verify the desired configuration and operation of the equipment are:
show int status
show etherchannel port
show lacp internal
show
Check that Core1 is root for VLAN 5 and 10, while Core2 is root for VLAN 20 and 99. Thus the ports in BLOCKING status on Core1 and Core2 should differ depending on the VLAN.
Design remarks
This topology offers high redundancy with very fast failure recovery. Independent of features like trunk failover or the NIC teaming, we reached in our tests recovery times of less than a second in optimum.
A drawback of this topology is that in some cases half of the bandwidth available between the IBM Eserver BladeCenter and the core is not used, due to constraints of the Spanning Tree
Algorithm blocking the traffic on the backup connections.
96Nortel Networks L2/3 Ethernet Switch Module for IBM Eserver BladeCenter
