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Beginner

DNAC Cluster Switching

Hi All,

 

I have been reading the Cisco DNA Centre Cluster and High Availability guide and it states that three switches should be used for DNAC connectivity to maintain cluster availability. This is because a DNAC cluster can only manage a single node failure, so if two DNAC servers were connected to the same switch, and that switch fails, the cluster will fail.

 

In most DC environments, customers usually have a pair of core or access switches so its a tough sell to try and install a third switch just for DNAC.

 

How much of an issue is this in reality? For example, if the switch that is connected to 2 DNAC servers fails causing the servers to disconnect from the network and for the cluster to fail, no network operations are impacted as DNA is not sitting in the control or data plane. In this scenario, do we just lose the ability to provision the network? If the switch failure cannot be resolved quickly, can we reconnect the impacted DNAC servers to the healthy switch to restore the cluster?

 

Thank you

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Beginner

Re: DNAC Cluster Switching

You can shut off all of your DNAC appliances without any major impact. While it’s down you won’t be able to make any changes and I also caution you not to remove any NADs while DNAC is down. Other than that nothing bad is going to happen.

My suggestion: put DNAC1&2 into SW1 and DNAC3 into SW2. Then configure ports in SW2 so that you can move your cables from DNAC1 or 2 to that switch if needed. For the cost of a couple of ports you save yourself from buying a switch. 

View solution in original post

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Enthusiast

Re: DNAC Cluster Switching

Hi,

You shouldn't connect DNA cluster devices to the same switch. Note that a cluster must be 3 DNA appliances and all ports for a single appliance in the cluster go to the same switch as shown in the diagram. This means three switches are required.DNA Cluster.JPG

Highlighted
Beginner

Re: DNAC Cluster Switching

Hi,

 

I understand that as this is clearly documented. My question is what is the real impact if I dont do as Cisco suggest as 3 switches (core or access) isn't the norm is most environments? Normally most DCs have a pair of core and access and not 3. In other words if I loose a switch and 2 appliances and the DNAC cluster fails, what is the real impact to the network? If there is no impact to data or control plane operations, then we can sustain a small outage whilst we repair the failed switch, or re-cable to a healthy switch. 

 

Thanks 

Highlighted
Enthusiast

Re: DNAC Cluster Switching

Hi,

DNAC doesn't affect the normal operations of your network, if it fails. If you can afford a 3-node cluster, I wonder why you can't connect them to your DC Access switches, which typically are more than 3, except your network is so small, in which case I wouldn't expect you to have a 3-node cluster. Anyway, the choice is yours.

Highlighted
Beginner

Re: DNAC Cluster Switching

You can shut off all of your DNAC appliances without any major impact. While it’s down you won’t be able to make any changes and I also caution you not to remove any NADs while DNAC is down. Other than that nothing bad is going to happen.

My suggestion: put DNAC1&2 into SW1 and DNAC3 into SW2. Then configure ports in SW2 so that you can move your cables from DNAC1 or 2 to that switch if needed. For the cost of a couple of ports you save yourself from buying a switch. 

View solution in original post

Highlighted
Beginner

Re: DNAC Cluster Switching

Thanks for the response. Very helpful

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