When we configure Network extension in HCX to extend the L2 between Source and Target Datacentre, HCX deploy Network extension appliance in both Datacentres. Once successfully deployed, VLAN will be extended.
In HCX, when we migrate VM (using L2 extension) from Source to target Datacentre, VM will communicate back to source Datacentre for inter Datacentre VLAN, outside datacenter and other required communication because gateway still exist at source Datacentre.
The problem you may face If you have many network intensive virtual workloads (from one of particular VLAN) to migrate to target datacentre then Network extension could be a bottleneck and workloads may experience latency issue.
It is always better to migrate all one respective VLAN (Lets VLAN ID-10) as quickly as possible and cutover that VLAN to start routing the traffic from Target Datacentre instead of source. Due to unavoidable circumstances, if you are not in position to migrate all VMs in limited timeframe and even experiencing latency issue then you must plan to extend the VLAN through physical switches by using OTV or similar extension method.
Another factors to be considered:
- Sufficient Migration link availability
- At least 10 G network speed (VMNIC) for both Source and Target Hypervisors
Dhiraj Dhall has more than 15 years of transformation delivery experience in cloud computing, infrastructure, dev-ops, microservices and container with larger global customers. He is a senior Architect and successfully delivered various kind of global project delivery such as greenfield, consolidation, SDDC and migration.