Policy-based IPSec VPN requires a VPN policy to be applied to packets to determine which traffic is to be protected by IPSec before being passed through the VPN tunnel.
This type of VPN is considered static because when a local network topology and configuration change, the VPN policy settings must also be updated to accommodate the changes.
When using a policy-based IPSec VPN with NSX-T Data Center, you use IPSec tunnels to connect one or more local subnets behind the NSX Edge node with the peer subnets on the remote VPN site.
When configuring NSX with both NAT and IPSec, it is important to follow the correct sequence of steps to ensure proper functionality. Specifically, configure NAT before setting up the VPN connection. If you inadvertently configure the VPN before NAT, for instance, by adding a NAT rule after your VPN session is configured, the VPN tunnel status will remain down. You must reenable or restart the VPN configuration to reestablish the VPN tunnel. To avoid this issue, always configure NAT before setting up the VPN connection in NSX or perform this workaround.
You can deploy an NSX Edge node behind a NAT device. In this deployment, the NAT device translates the VPN address of an NSX Edge node to a publicly accessible address facing the Internet. Remote VPN sites use this public address to access the NSX Edge node.
You can place remote VPN sites behind a NAT device as well. You must provide the remote VPN site's public IP address and its ID (either FQDN or IP address) to set up the IPSec tunnel. On both ends, static one-to-one NAT is required for the VPN address.
IPSec VPN can provide a secure communications tunnel between an on-premises network and a network in your cloud software-defined data center (SDDC). For policy-based IPSec VPN, the local and peer networks provided in the session must be configured symmetrically at both endpoints. For example, if the cloud-SDDC has the local networks configured as X, Y, Z subnets and the peer network is A, then the on-premises VPN configuration must have A as the local network and X, Y, Z as the peer network. This case is true even when A is set to ANY (0.0.0.0/0). For example, if the cloud-SDDC policy-based VPN session has the local network configured as 10.1.1.0/24 and the peer network as 0.0.0.0/0, at the on-premises VPN endpoint, the VPN configuration must have 0.0.0.0/0 as the local network and 10.1.1.0/24 as the peer network. If misconfigured, the IPSec VPN tunnel negotiation might fail.
| Edge Node Size | # of IPSec Tunnels Per VPN Session (Policy-Based) |
# of Sessions Per VPN Service | # of IPSec Tunnels Per VPN Service (16 tunnels per session) |
|---|---|---|---|
| Small | N/A (POC/Lab Only) | N/A (POC/Lab Only) | N/A (POC/Lab Only) |
| Medium | 128 | 128 | 2048 |
| Large | 128 (soft limit) | 256 | 4096 |
| Bare Metal | 128 (soft limit) | 512 | 6000 |
For information about configuring a policy-based IPSec VPN, see Add an IPSec VPN Service.
