DNA: BGP AS Number change for a Fabric

[Daniele Metta]

Hi,

Please: is it possibile and supported to change the BGP AS Number already in place for a Fabric (configured for the Borders of the Fabric) ?

Actually now the Fabric Border Nodes haven't any neighbourship (due to other reasons...), so now A part from the "reconfig" related to the Border config, no bgp neighborship would be broken.

thank you

Daniele

[Daniele Metta]

Considering I didn't receive any reply, I would ask if the following procedure could be supported in order to change the BGP AS Number already configured on Border Nodes of a SDA Fabric (without cleaning all the Fabric config apart from the BN config):

Situation: SDA Fabric with 2 CP/BN (Node-A and Node-B)

• Remove the first CP/BN Node-A from Fabric
• Reconfigure the Node-A as CP only
• Remove the second CP/BN Node-B from Fabric
• Reconfigure the Node-B as CP only
• Configure the Border Node feature on both CPs with new AS Number

Of course during the removal of the Boder Node roles, underlay connectivity must be maintaned to let DNAc manage the changes on the two nodes.

Please let me know what you think

Thank you

Daniele

[jedolphi · Accepted solution]

Hi Daniele, there is no easy way to change the BGP ASN in an operational SD-Access Fabric site. The BGP ASN is set during the initial site instantiation. Regarding your proposed procedure, I tested it in the lab, BGP is deployed to the dedicated CP Nodes, so deleting both BNs wont undo the entire BGP configuration, meaning it can't be changed using the sequence you've proposed. You'll need to decommission the entire Fabric Site and recreate it using your desired ASN. I realise this might not be the answer you want to hear, if so please contact your sales team to provide feedback and also "Make a Wish" in the DNA Center UI via the question mark menu in the top right corner. In the wish please share details about why this is needed so the Product Managers have sufficient context to prioritise appropriately. Cheers, Jerome

[Daniele Metta]

Again really thank you Jerome!

I will follow that way. And yes, you are right decomissioniing the entire fabric is not practicable for us.

But I am wondering: in case I manually clear all the remaining BGP configs on BN/CP after the removal from Fabric (for the time up the moment they will be again BN and configured correctly for ASN, and keeping them reachable via other static or dynamic routing to DNAc) isn't something valid ?

[jedolphi · Accepted solution]

Hi Daniele, I tested manually removing the remaining BGP configs and it does indeed work! Generally the developers tell us to never remove configs deployed by DNA Center, so while it works, it's in the "grey zone" with respect to engineering and TAC support. It's up to you how you want to proceed: if full TAC and BU support is needed while you make this change then I'd ask you to contact your SE or AM to negotiate that please. If you don't know who that is then please send me the end customer name and location. Regards, Jerome

[Daniele Metta]

Again Thank you Jerome, and "almost bingo"....
I will check this way and for sure I will ask to TAC if this is the feasible way to proceed (we have support and contacts).

But I really want to thank you for your kind support!

Daniele