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Virtual Connect Domain uplink question

Trusted Contributor

Virtual Connect Domain uplink question

Pedrag had a customer question on uplinks:




Customer asked me is it possible to connect two Blade chassis, one with FlexFabric, second with Flex10 but without stacking links.


I would say that this is not possible since VC is not module with classic switch functions and that only way to connect them is by use of stacking links.


Am I right or ?




Reply from Aleksandar:




You can have this configuration by directly connecting the two VC domains.

You can use dedicated port or make SUS and configure teams.


The limitation is of course that the traffic on this link is entirely internal for the enclosures.




Input from Robert:




Aleksandar is correct, too, but we are both guilty of simplification.


If each enclosure is an independent VC domain, you can have an “uplink” from the VC domain in each enclosure to the VC domain in the other enclosure.  This uplink can carry a single network (e.g. heartbeat LAN or live migration LAN) or multiple networks with a Shared Uplink Set.  However, you cannot have more than one uplink for any network active on a VC domain at any time, so the networks that you put on the “uplink” between the two enclosures will be contained in the enclosures and can’t be connected to any external devices in the data centre.  This is 100% fine for heartbeat LANs and similar, where you only want the blades in the two enclosures to be connected to each other and nothing else.  You can have multiple uplinks between the two enclosures for resilience in the usual Active/Active and Active/Passive arrangements.  The loop protection mechanism will work fine to prevent multiple active paths in the same networks.


You can then define other uplinks or Shared Uplink Sets that connect to the rest of the data centre networks, but do not carry the heartbeat LANs, Vmotion LANs, etc., and they will work fine, too.  Again, you can have all the usual resilience features for these uplinks.


However, if you carry the heartbeat LANs or Vmotion LANs in the “uplinks” between the enclosures and the uplinks to the rest of the network, one set of uplinks will block: VC will not allow more than one active uplink per network per VC domain.


This is a perfectly acceptable and supported design, to the best of my knowledge.




Comments or questions?