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Can uplinks from different Virtual Connect Flex-10 modules compose trunking by LACP?

Trusted Contributor

Can uplinks from different Virtual Connect Flex-10 modules compose trunking by LACP?

Peng was looking for some informaiton on LACP and trunking of the Virtual Connect uplinks to external switches:



Hi experts,


This is Peng from TECHub and sorry for disturbing you.


We received a question that, can uplinks from different VC Flex-10 modules compose trunking by LACP.

These uplinks are connected with Cisco switches and LACP configured at these Cisco switches.


I know, also am told in these PDLs that, up to 8 ports from a VC module can form a LACP group,

which is limited to a single VC module and cannot span two modules,  


The document below seems to be a evidence, too.

è  P.57  4th paragraph


  When multiple uplinks are used on a network, HP Virtual Connect Manager first verifies if any of the ports

  can be collected together into an aggregation group (requires connections to go from a single Virtual

 Connect Ethernet module to a single data center switch)……



But, what about the following documents,

è  P.20  1st paragraph


 When some of the uplinks configured within a vNet connect a VC module to different upstream switches,

 or from multiple VC modules to a single or multiple switches, some links will be active and the remaining

 will be Standby, potentially providing additional bandwidth as well as increase availability, using Link Aggregation Protocol (LACP


 ** figure 1-10 in page 22 shows that 4 ports compose trunking, for ports from VC#1 are all standby.


Would you please tell me answers if you know? Thanks in advance!!


  1. uplinks from different VC Flex-10 modules compose trunking by LACP? (origanal question)
  2. do I confuse something when reading 2 manuals mentioned above, e.g., LCAP/trunking and LCAP group?




Rui stepped up to provide Peng some guidance:


I believe that the rules has not changed.


There are 4 baseline rules to compose a trunk with LACP. The connections must respect:


                1st – Same Origin (same VC module)

                2nd – Same Target (same destination Switch)

                3rd – Same Speed (you cannot trunk 1GB uplinks with 10Gb uplinks)

                4th – Target Switch must support LACP


If you need the bandwidth, you can use an active-active configuration by creating two distinct VNET (in VC) and assign one to the trunk from VC1 and the other to the trunk from VC2. After that you just have to configure on port from the server to VNET1 and the other to VNET2 and establish a Transmit Load Balancing Team on the server.


Hope this helps.


Ramy also joined the conversation:


Hi Peng,

You are confusing between LACP and Spanning Tree protocols. Rui’s message below is confirming the rules of how to setup a LACP link between a VC and a Switch, also he provided a very good scenario to avoid SPT behavior.


Below details may help to clarify your confusion:

  • LACP is a layer 2 “standard” link aggregation protocol that should work with every device that can support LACP. VC, HP Switches and Cisco Switches can support LACP
  • You can aggregate up to 8 physical ports in one logical port as a trunk link between single source and single destination. It is called aggregate link in HP and Ether Channel in Cisco. It will work as one single logical port and all the physical ports forming this link will be active.
  • Spanning Tree protocol is a loop prevention Layer 2 protocol. It works to put some of the ports in standby mode when you have multiple paths between single source and single destination to prevent Layer 2 loops. There are 5 different protocols (STP, RSPT, PVSTP, PVSTP+, MST) that have been developed, some are standard and some are Cisco proprietary. VC does not support SPT as it has its own L2 loop prevention mechanism.



Does this provide what you need? Other comments or suggestions? It seems that LACP, NIC teaming, and trunking all seem to get people's interest and need for advice.

Alejandro Gomez Lopez
Occasional Contributor

Re: Can uplinks from different Virtual Connect Flex-10 modules compose trunking by LACP?

Sorry to bring up this old post, but I would like to know if the restriction that a LACP link cannot span two interconnect modules will be removed any time in the future.


Some of our customers have external switches that do not tolerate active-active configuration featuring two different LACP links (each from a different VC module) due to MAC-port association issues. In these cases, being able to form a single LACP aggregation spanning two modules would be a very interesting addition.


Many thanks in advance.