There are three steps to creating BGP filters in NSX-T:
- Create an IP Prefix for “ANY” and each tenant subnet.
- Create a IP Route Map
- Apply the Route Map to the T0 Router Uplink
An IP prefix list contains a single or multiple IP addresses that are assigned access permissions for route advertisement. If there are multiple IP addresses in this list are processed sequentially. IP prefix lists are referenced through route maps with in or out direction.
For example, you can add the IP address 172.16.10.0/24 to the IP prefix list and deny the route from being redistributed to the northbound router. This means that with the exception of the 172.16.10.0/24 IP address all other IP addresses are going to be shared the router.
You can also append an IP address with less-than-or-equal-to (le) and greater-than-or-equal-to (ge) modifiers to grant or limit route redistribution. For example, 192.168.100.3/27 ge 24 le 30 modifiers match subnet masks greater than or equal to 24-bits and less than or equal to 30-bits in length.
The default action for a route is Deny. When you create a prefix list to deny or permit specific routes, be sure to create an IP prefix with a blank network address and the Permit action if you want to permit all other routes.
- From your browser, log in to an NSX Manager at https://nsx-manager-ip-address.
- Select Routing from the navigation panel.
- Select the tier-0 logical router.
- Click the Routing tab and select IP Prefix Lists from the drop-down menu.
- Select Add.
- Assign a name for the IP prefix list.
- Click Insert Row to add a network address in the CIDR format. For example, 192.168.100.3/27.
- Select Deny or Permit from the drop-down menu. You grant or deny each IP address from being advertised, depending on your requirement.
- (Optional) Set a range of IP address numbers in the le or ge modifiers.
- Click Save.
- The newly created IP prefix list appears in the row.