Prioritize Tunnel Static Route over L2 physical route

O.ELHANCHI — Mon, 09 Jan 2023 12:56:54 GMT

Hi,

I have an IPSec Tunnel between a remote central site and a PA-220.

This tunnel advertises it's remote internal network in 10.100.10.0/27.

A static route has been created in the PA with a metric > 1 (10), to route traffic in direction of 10.100.10.0/27, through the IPSec tunnel interface, tun.254.

This route is effectively working, as an ICMP trace shows traffic flowing from the tunnel local IKE Peer interface (172.X.X.X) to a remote network host (10.100.10.15).

Now here is where things gets problematic, we also have a physical network directly connected to the PA appliance, covering all the range of the 10.0.0.0/8 subnet.

As such this creates by default a route with a metric of 0, which directs all traffic in direction of 10.0.0.0/8 through the physical interface that is connected to that network, as you may observe in the 2nd row of the following table :

As 10.100.10.0/27 is included within 10.0.0.0/8, this rule (2nd row) takes precedence over my tunnel static route (3rd row), and therefore, the traffic that should be tunneled is routed through the physical interface (10.255.2.62), and never find it's proper destination.

In concrete terms, a local device that is behind the firewall would be unable to contact a remote host in the 10.100.10.0/27 network (10.100.10.15), because of this metric issue.

I am aware this is keen to a design problem in the infrastructure, but I am just wondering how to engineer a solution to make such communication possible, a solution that doesn't involve changing existing addresses.

Kindly yours

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Re: Prioritize Tunnel Static Route over L2 physical route

Raido_Rattameister — Mon, 09 Jan 2023 13:36:39 GMT

Try to change metric of second route to 10.

As /24 mask is more specific then this routing logic should work without issues.

Re: Prioritize Tunnel Static Route over L2 physical route

O.ELHANCHI — Mon, 09 Jan 2023 14:03:53 GMT

Hey,

Would love to do just that, however that route is not static, it got added by the PA automatically after assigning an address to the corresponding interface.

I am investigating the CLI as it seems impossible to edit in the UI.

Thanks

Re: Prioritize Tunnel Static Route over L2 physical route

Raido_Rattameister — Mon, 09 Jan 2023 14:06:52 GMT

Policy Based Forwarding is checked before routing table.

If you have PBF to send 10.100.10.0/27 into the tunnel then virtual router is not checked for IPs in that subnet.

topic Prioritize Tunnel Static Route over L2 physical route in General Topics

Prioritize Tunnel Static Route over L2 physical route

Re: Prioritize Tunnel Static Route over L2 physical route

Re: Prioritize Tunnel Static Route over L2 physical route

Re: Prioritize Tunnel Static Route over L2 physical route