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Live VM Mobility Network Requirements

Every time someone mentions how awesome new technologies solve live VM mobility across WAN networks, I start muttering unmentionables. Live VM mobility across disjoint layer-2 subnets works great in demos, but usually fails in real life due to stale ARP caches. The only way to solve this problem for good is to implement EC2-like layer-3 forwarding in hypervisor soft switches.

Update: LISP Host Mobility seems to be a potential exception; see the comment from Nico.

For more details, watch the VM Mobility Requirements video (part of Enterasys-sponsored DCI webinar), read the Hot and Cold VM Mobility blog post or watch the recording of NFD4 session with Cisco’s Victor Moreno.


  1. Hello Ivan,

    From what I've seen when playing with LISP ASM (host mobility accross subnets), the stale ARP caches resident in other VMs in the same subnet are cleared by a gratuitous ARP sent by local XTR devices so that on-subnet server to server traffic is then LISP encapsulated.

    1. That sounds cool, but the moved VM also has an ARP cache. How is that one flushed/replaced?

    2. Use anycast gateway.


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