First time upgrade ACI

[Mahmoud]

hello

this is my first time to upgrade ACI from current version 2.3 to 4.2 with multi pod topology

ACI is used as L2

 VMM integration is used with hyper-v and vmware

most of our critical services are running from pod-1

I read a lot of documents from cisco official and blogs but still have some concerns

1.  CIMC upgrade is mandatory?
2. can I upgrade pod-2 first from 2.3(1) → 3.1(2) → 4.1(2) → 4.2(4) then upgrade pod-1 from 2.3(1) → 3.1(2) → 4.1(2) → 4.2(4)?
3. can fabric run with different versions (APIC use same new version but switches use different version old/new) if I plan to upgrade at two days or more?

[Sig Nine]

Hello, Mahmoud.

> CIMC upgrade is mandatory?

You also need to upgrade CIMC to get proper support.

> can I upgrade pod-2 first from 2.3(1) → 3.1(2) → 4.1(2) → 4.2(4) then upgrade pod-1 from 2.3(1) → 3.1(2) → 4.1(2) → 4.2(4)?

Yes, you can upgrade the version of each switch with different pods.

> can fabric run with different versions (APIC use same new version but switches use different version old/new) if I plan to upgrade at two days or more?

For a short while during the version upgrade work, I think it is inevitable to work with different versions. However, it is recommended to get the same version as soon as possible.

Regards,

[Sergiu.Daniluk]

Hi @Mahmoud 

I just want to add few details on top of what @Sig Nine and avoid confusion and potential problems in your network:

> CIMC upgrade is mandatory?

You will have to check the compatibility matrix for the target version:

https://www.cisco.com/c/en/us/td/docs/switches/datacenter/aci/apic/sw/4-x/release-notes/cisco-apic-release-notes-424.html#_Toc27555308  (miscellaneous compatibility information) - you have there a list of supported version of CIMC depending on APIC model you have.

> can I upgrade pod-2 first from 2.3(1) → 3.1(2) → 4.1(2) → 4.2(4) then upgrade pod-1 from 2.3(1) → 3.1(2) → 4.1(2) → 4.2(4)?

NO. Definitely no. You can have at most 2 different releases in the fabric at any given time. The entire fabric (both pods) must be upgraded to each intermediate release before any one element is upgraded to the next hop. This means upgrading the APICs and then upgrading the switches to each intermediate release. Also, keep in mind that you cannot upgrade only one APIC out of the cluster to a specific version. So when you set the upgrade to version X for apic, all APICs (from all pods) will upgrade to that version.

> can fabric run with different versions (APIC use same new version but switches use different version old/new) if I plan to upgrade at two days or more?

You can run the fabric with 2 different versions (keeping in mind the answer to previous Q) but for production networks, you should keep this version mismatch at a minimum possible and avoid doing config changes during this time to avoid potential issues.

Stay safe,

Sergiu

[Mahmoud]

Hello @Sig Nine @Sergiu.Daniluk 

many thanks for your valuable feedback

so I have to upgrade the whole fabric as below sequence

1. POD 2>> 2.3(1) → 3.1(2)
2. POD 1>> 2.3(1) → 3.1(2)
3. POD2>> 3.1(2) → 4.1(2)
4. POD1>> 3.1(2) → 4.1(2)

still have two concerns

1. CIMC upgrade should be done for every upgrade or we can upgrade directly to intended version 

I mean that

          APIC with version 3.1 recommend CIMC 3.0(3f) version

          APIC with version 4.2 recommend CIMC 4.1(1f) version

so do we need to upgrade as below options

Option 1: upgrade CIMC to version 3.0(3f) before APIC upgrade to 3.1 version and then upgrade to version 4.1(1f)    before upgrade APIC to 4.2.

option 2 :  we can upgrade CIMC  directly to version 4.1(1f)

======================================

another concern, all of our critical services are active at pod-1 so I have to make the services active at pod 2 during upgrade pod-1 (that's why I asked before to upgrade pod-2 to the latest version then upgrade pod-1 to eliminate service flapping between both pods)

all of my servers,firewalls,routers are connected via vPC architecture so based on cisco documents no service interruption should happened during upgrade if I divide switches in different groups during upgrade.

my question in this point is how can I make sure that no service interruption will happened during restarting switches during the upgrade (note: I already did a test by restarting one of switches in vPC domain and no services interruption happened ). in other words restating switch with same version is the same behavior with restarting switch during upgrade with new version.