View Full Version : HP Lefthand networks P4300 SAN ALB (adaptive load balancing) Question

04-28-2010, 4:54 PM
Food for thought:

We have a P4300 SAN connected to two Cisco 2960 switches. Each switch is connected to the network core (4506) through a trunk connection. Each NIC on each SAN is connected to one Cisco switch. So there are two SAN nodes and two switches, each SAN node has a connection to both switches, All VLAN operations appear to be working

We when power down one switch both SAN nodes remain connected (This is good), however when we unplug the switch trunk port connection, one of the SAN nodes becomes unreachable (This is bad). Now the interesting thing is when we disconnect the other trunk port on the other switch the other SAN node becomes unreachable while the other remains active.

Again , if one of the switches or Ethernet ports gets turned off the failover seems to work fine. Disconnecting the trunk seems to produce a strange result

Is this behavior expected ?

04-29-2010, 10:35 AM
Follow up: It turned out to be a spanning tree issue. We had portfast enabled on the iSCSi vlan interfaces. Disabling portfast inconjuction with a trunk cross connect between switches, resolved the issue.

Now when we unplug the trunk connection to the core both storage nodes stay up.

04-29-2010, 12:06 PM
Thanks for the follow up.

Nice little setup you have there. :)

04-29-2010, 1:26 PM
Truthfully I was a bit embarrassed as I didn't initially think about spanning tree. We did turn on portfast when we connected the SAN nodes thinking it was a good practice. But we applied the config to all the interfaces in the iSCSi vlan. Sometimes it’s the obvious things that get you in trouble, if it was a snake it would have bitten me sort of thing.

We are pretty excited about the project. We are taking 30 physical servers down to 3 ESX hosts, with iSCSi SAN storage.