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Virtual Connect Flex-10, Cisco HSRP, and OSPF question

Trusted Contributor

Virtual Connect Flex-10, Cisco HSRP, and OSPF question

Ricardo had a fairly complex networking question:




We have a question floating around about the HP flex-10, and how it will act if set up like the attached power point. In it, we have a VLAN (Vlan 10), and we have VMs talking on Vlan 10.  If the LACP trunk between the Network switches goes down, what is the expected network response?  Does the Flex-10 participate in spanning tree? Is one of the uplink ports in some sort of blocking mode?




Cullen joined the discussion:




Are the two trunks in a single shared uplink set?


If they're in two shared uplink sets, then both paths will always be up.  There is no failover from a Virtual Connect perspective, as they're two separate shared uplink sets.  Any failover will have to be handled by the individual servers.


If they're in one shared uplink set, then one uplink will be in standby and the other will be active.  If the active link goes down, the other link will become active.  There may be some delay in populating the switch tables on the upstream switches until the servers send a packet (either because they're sending on their own or have been ARPed).


Virtual Connect does not participate in Spanning Tree; it uses its own proprietary loop prevention.




Then Hongjun replied:




I think customers is asking what will happen if the LACP bundle between two Cisco Switches goes down.


So no state change on Flex-10 SUS. Flex-10 has no idea what's going on between Cisco switches.


On Cisco switch, if that LACP channel is the only way HSRP talking, then he'll get both switches HSRP active and can forward the traffic from VC to northbound network, for return traffic, both routers can forward traffic as well if they advertise OSPF routes to core.


Just think two switches connecting to a  "big server with 2 NICs". There is no blocking/unblocking going on VC side.




Other input or comments on this situation?