The Overlay Addressing Scheme for the SD-WAN (relevant for releases lower than 21.1.1)


Versa Director has introduced a new overlay addressing scheme that provides greater flexibility in configuring the SD-WAN overlay addresses in Labs, for POCs, and field deployments. Post the Versa Director installation:

  1. Login to the Versa Director GUI. 
  2. Select Director Context > Administration > SDWAN > Settings to see the overlay address scheme information.
  3. Click Edit button in the Overlay Address Scheme section to modify the overlay address scheme configuration. This opens a Confirm window.
  4. Click OK. This opens the Edit Overlay Addressing window.

    Field    
    		Description
    IPv4 Prefix
    		Specify the new IPv4 Prefix. The default is set to 10.0.0.0/8
    Maximum Organizations
    		Specify the new number for the maximum organization. The default is set to 512.

  5. Log into the CLI mode and run the set nms sdwan overlay-address-scheme ipv4-prefix <ip-address> maximum-organizations <count> CLI command to select any IPv4 addressing space and configure the maximum number of orgs you want to support.
    Example:
    Administrator@vd1%set nms sdwan overlay-address-scheme ipv4prefix 18.28.0.0/15 maximum-organization 130


  6. Run the show nms sdwan overlay-address-scheme CLI command to view the current overlay address scheme.
    Example:
    Administrator@Director-Active% show nms sdwan overlay-address-scheme 
ipv4-prefix           18.28.0.0/15;
maximum-organizations 130;


Detailed Explanation of the Calculation

When you select prefix-length and the number of organizations, ensure that the prefix_length + log2(max_orgs) is not more than 24. This ensures supports for at least 128 devices.

Figure1: Diagrammatic representation of the calculation.


 NOTE: Release 16.1R1 S1 and earlier, use the default 10.0.0.0/8 address space with up to a maximum of 512 tenants/org. 


From release 16.1R1 S2 onwards, Versa introduces a new address scheme that allows you to configure any IPv4 address prefix and specify the maximum number of orgs for deployment for the flexible overlay address scheme. 


The org-id is encoded in the overlay address in the next n bits after the prefix length, where n is log2 (max-orgs).

The MSB of the 1st byte from LSB is used for ESP bit encoding. The remaining 7 bits are used for device-id encoding.

For Example: 

If you specify the overlay address as 15.1.128.0/17, and max-orgs as 128 then:

  • org-id is encoded in first 7 bits of the 3rd octets from MSB. 
  • The bit after org-id bits is used to encode ESP or VXLAN address. 

In this example:




The Modified Overlay Addressing Scheme (IPAM based) starting 21.1.1


(In Releases 21.1.1 and later.) Versa Director supports IPAM-based IP address allocation for device overlay tunnels (ESP and VXLAN) and for staging IP address pools on Controllers and hub controller nodes (HCN). IPAM is an internal service on Versa Director and runs as a container. The main features of IPAM-based addressing allocation are:


1. Organization ID and device ID are not encoded in the IP address allocated to a device

2. You can add multiple smaller address pools in the overlay addressing configuration based on your requirements. With IPAM, you can deploy an SD-WAN network with a small overlay IP pool or pools: a /8 or /16 prefix is not required.

3. The next available address in the pool is allocated to a new device being created.

4. When you upgrade Versa Director, currently configured overlay address pools and allocated addresses are migrated automatically to the IPAM module.

5. During the upgrade process, if the validation script finds that an address is allocated to multiple devices, the upgrade process fails. You must rectify duplicate addresses before attempting an upgrade.



To configure a overlay address schema follow the below steps 

(Note: that if you do not configure an IPv4 prefix before you deploy the first Controller node in the network, the default overlay prefix, 10.0.0.0/8, is used. After you deploy the first Controller node, you cannot modify or select which overlay prefix to use. Therefore, if you want to use a different overlay prefix, configure and deploy it immediately after you install the Versa Director)



1. In Director view, select the Administration tab in the menu bar.

2. Select SD-WAN > Settings in the left menu bar. The main pane displays the Device Settings and Overlay Address Prefixes panes.



3. Click the + add icon in the overlay prefixes context, below window would pop up where you can enter the prefix you want to use



4. To check the statistics pertaining to a prefix, just click on the relevant prefix in the overlay address prefixes pane, it will display a screen as below