Firepower IPSEC VPN tunnel issues with Remote ACL

When you work with Cisco Firepower firewall systems, you may come across issues related to ACLs. What happens is Firepower systems drop any remote traffic even if the correct ACLs are in place. To resolve this issue a workaround can be applied. 

The parameter is sysopt connection permit-vpn can be enabled. On ASA systems, this is enabled by default. But not on firepower systems. We will look at how we can enable this parameter on Firepower Device Manager (FDM).

Go to FDM GUI > Device > Advanced Configuration > View Configuration

Click on FlexConfig Objects and click on the ‘+’ icon to create a new FlexConfig object, give it a name

Click on the ‘+’ icon for the ‘Variables’ section. Give the variable any name, and select ‘string’ as its type. Enter ‘sysopt’ (without quotes) as the value, and click ok.

In the template section, type {{vpnSysVar}} connection permit-vpn

Go to Flexconfig policy and add the newly created Flexconfig object. 

Finally, Save and deploy the changes. 


Policy-Based VPN vs Route Based VPN

When we are planning for VPN solutions, we should have an understanding of 2 VPN solutions (Policy Based and Route Based). 

Policy-based VPNs encrypt a subsection of traffic flowing through an interface as per configured policy in the access list. The policy dictates either some or all of the interesting traffic should traverse via VPN.

A Route-based VPN works on routed tunnel interfaces as the endpoints of the virtual network. All traffic passing through a tunnel interface is placed into the VPN. Rather than relying on an explicit policy to dictate which traffic enters the VPN, static and/or dynamic IP routes are formed to direct the desired traffic through the VPN tunnel interface.

To summarize, let’s see a comparison table with the main differences between Policy-Based and Route-Based VPN solutions.

Policy-based VPN Route-based VPN

Supported on most network devices (Cisco Routers, Cisco ASA, other vendors, etc)

Supported only on Cisco IOS Routers. Very limited interoperability with other vendors

Routing Protocols cannot pass through the VPN tunnel

Routing Protocols can pass through the VPN tunnel

Strong Security natively

Need additional configuration

Complex Configuration

Simplified Configuration

Supports P2P network topology while Hub and Spoke topology is not supported Supports Hub-spoke , P2P and P2MP network topologies
Traffic flowing through the VPN tunnel can’t be NATTed Traffic flowing through the VPN tunnel can be NATTed since it passes through either the tunnel interface or gateway IP address specified as next-hop in routing.
VPN failover group provides redundant VPN tunnels. SD-WAN policy routing with backup gateway configuration provides redundant routes.
Small networks with limited network expansion. Large networks experiencing rapid growth.