HP’s Virtual Connect supports a feature called Smart Link, a network enabled with Smart Link automatically drops link to the server ports if all uplink ports lose link. This feature is very similar to the Uplink Failure Detection (UFD) that is available on the HP GbE2, GbE2c and most ProCurve switches. I believe there is a similar feature available on Cisco switches called Link State Tracking.
You might be asking, so what. Well a reader recently mentioned Smart Link in conjunction with my post concerning HP Virtual Connect & vSphere 4 so I thought I’d post some of my thoughts about Smart Link. It’s seems redundant to me given the presence of LACP but let me explain.
From a Nortel perspective you can connect two NICs from a single server to a Nortel switch cluster, two ERS 5500 or 8600 switches, using LACP and get a “802.3ad Dynamic with Fault Tolerance” configuration. This essentially provides an active/active solution utilizing both NICs to their fullest. LACP is used to determine network path failures.
From a Virtual Connect perspective the same applies as above. The Virtual Connect Ethernet interconnect modules act as a single switch fabric allowing you to create a “802.3ad Dynamic with Fault Tolerance” configuration providing an active/active solution. While you can do this to servers you can’t span external uplinks across interconnects out of the enclosure in an active/active configuration.
In the old days you’d only get a “Transmit Load Balancing with Fault Tolerance” or “Network Fault Tolerance” configuration when your server NICs spanned two switches. This essentially provided an active/standby solution. Network Fault Tolerance only uses link status as a determinator to whether the network is functional or not. In order to detect a failure the server would need to see a link loss on the primary NIC before failing over to the standby NIC. Smart Link provides the ability to shutdown the server switch ports if all the uplink switch ports go down so the NIC teaming configuration can detect the link status change on the server and fail-over to the standby NIC which would be cabled to a different network switch.
In this case it would appear to me that LACP has really replaced what I would describe as a legacy feature, Smart Link. You can have multiple external uplinks out of an enclosure spread across multiple interconnects. While only the external uplinks on a single interconnect will be active, any remaining uplinks on any other interconnects will be in a standby mode.
I’m telling this as I see it, I’m no expert concerning Virtual Connect by any means so please tell me if I’m wrong!