Migration to Cisco ACI Data Center

netbeginner · ‎12-09-2019

Dear Experts,

We are about to start traditional data center migration to new ACI data center migration, I have searched and gone through many documents available on internet but they all are more towards theoretical aspects . As i am new to Migration with ACI and looking for expert advise from you all with some practical technical approaches to avoid any unwanted service disruption during migration.

Some basic details are as:

1- Very Important point - here is :Have to retain the same VLANs on new data center (ACI) which are there in existing data center". for this we are proposing L2 links between Old and New data Center for migration purpose. but feels that we may stuck with this approach anytime.

2- What would be the best approach for DNS services migration.

3- In existing data center we do have Load Balancer also (for Internal & External traffic), What would be the best and practical approach to migrate these LB services.

4- What were other things that need to taken into considering while during migration on data Center, especially in ACI aspects.

Will add if anything missed up.

Rgds

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Claudia de Luna · ‎12-09-2019

Hi @netbeginner,

This can be done.

1. I always like to configure both L2 links for the VLAN "extensions" into ACI and workload migrations and L3 links to your "core" or primary L3 routing point. This lets you follow this type of workflow.

its a good idea to establish compute and storage on your ACI fabric first if you are moving virtualized workloads. Some of my clients buy some new compute and storage for ACI, some clear off workloads on existing compute and move them over (storage can be tricky here so make sure you understand how your storage is going to work during this migration period)
Now that you have L2 connectivity and compute and storage you can start moving VMs (or bare metal servers) over to ACI (for example, you could move your secondary DNS server)
- In this case your Bridge Domains are strictly layer 2 (not optimized so the mimic traditional flooding behavior) and do not advertise a gateway
Say you start with Vlan 100, at some point you have moved enough servers over that you want to flip the gateway on to the ACI Bride Domain. At that point you enable unicast routing on your Bridge Domain and you associate your L3Out to your Vlan100 EPG. Be careful of the gateway Mac it will change (and may cause slight disruption) unless you take steps to keep it. Now your Vlan100 subnet is reachable via your L3 connection into ACI (and not L2)
- Note: You have to make the proper routing changes on your old infrastructure
Keep going until you have moved all your workloads and physical servers off your old infrastructure.
Its important to get commitments form the server team and application owners to move or you will be stuck like this for some time.
Be clear about when the old infrastructure needs to be decomissioned.

2. See scenario above.

3. This is a big topic. The least impactful approach is to keep the same design. You should be able to support in in ACI.

4. For a migration like this you do want to make sure you build out your Bridge Domains to mimic traditional flooding behavior and you want them at L2 only to begin with as I mentioned in the scenario for #1.

With careful planning you can have a very low impact migration.

Make sure you test!!

netbeginner · ‎12-09-2019

Hi Claudia,

Thanks a ton !! for response and suggestions.

Could you pls elaborate more on point - " Say you start with Vlan 100, at some point you have moved enough servers over that you want to flip the gateway on to the ACI Bride Domain. At that point you enable unicast routing on your Bridge Domain and you associate your L3Out to your Vlan100 EPG. Be careful of the gateway Mac it will change (and may cause slight disruption) unless you take steps to keep it. Now your Vlan100 subnet is reachable via your L3 connection into ACI (and not L2)"

Also, requesting if You or anyone can share any document or article or whitepaper which describes more about migration approaches with examples rather then theoretical bullets points on migration approaches.

Rgds

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