Loopback Interfaces in VPNs

[SDorsey]

In my configs, I generally reference the actual egress interface on the PAN device. I have run across some configs where the original engineer tied the GP portal to a loopback interface which basically just pointed to the same IP tied to the egress interface. Is there a benefit to using the loopback instead?

[HULK · Accepted solution]

Hello Mackwage,

The loopback interface is an independent logical interface of a device. It will be useful, If you want to host any other service, that would be accessible by both internal as well as external network. So, even though the external interface is down, the services will be accessible from internal subnets ( Loopback will be up).

But If you want to host on an external egress interface, the service will not be available from the internal subnet while the  external interface is physically down.

Hope this helps.

Thanks

[UhMayYeah]

I believe you are referring to the following test cases:

Can GlobalProtect Portal Page be Configured to be Accessed on any Port?

Access to GP Portal need open access to port 443 on the external interface IP which can make it vulnerable. For additional security loopback interface can be used to host GP services on a non-default port , where a GP user connects to GP portal on an external IP + non-default port socket which gets translated to loopback + port 443.

How to Configure Global Protect Gateway On Loopback Interface with iPhone Access

Exhibits how non-ssl services like Outlook web access can be hosted External IP using Loopback.

HTH..!